ios: Update launch screen.

Use a "Storyboard" instead of an "XIB", as has apparently [1] been
required since 2020-04-30. A change like this is part of the RN
v0.62 -> v0.63 changes to the template app [2], corresponding to
facebook/react-native@33b3a1a14.

Since it's simple to do (especially after adding the "Brand" color
set in a recent commit), make it be a solid brand-color screen
instead of solid white. It should match the color of our
`LoadingScreen`, which is often the first thing that displays when
you open the app.

The changes in this commit coincide with the iOS-specific
instructions from `expo-launch-screen` for how to set up a launch
screen [3], with some exceptions:

- We don't actually go on to set up `expo-launch-screen`; we
  currently don't intend to [4].

- We don't do anything marked "optional".

- We don't add an image to the launch screen; we can do that later
  if we want to.

- We set the `Storyboard ID` to `LaunchScreenViewController`, not
  `SplashScreenViewController`. Apple regularly calls the thing a
  "launch screen", not a "splash screen".

[1] https://developer.apple.com/news/?id=03042020b
[2] https://react-native-community.github.io/upgrade-helper/?from=0.62.2&to=0.63.3
[3] https://github.com/expo/expo/tree/master/packages/expo-splash-screen#manual-configuration
[4] https://chat.zulip.org/#narrow/stream/243-mobile-team/topic/React.20Navigation.20v5/near/1042794
[5] https://developer.apple.com/design/human-interface-guidelines/ios/visual-design/launch-screen/

Author: chrisbobbe

ios/ZulipMobile.xcodeproj/project.pbxproj

@@ -8,10 +8,10 @@
 
 /* Begin PBXBuildFile section */
 		13B07FBC1A68108700A75B9A /* AppDelegate.m in Sources */ = {isa = PBXBuildFile; fileRef = 13B07FB01A68108700A75B9A /* AppDelegate.m */; };
-		13B07FBD1A68108700A75B9A /* LaunchScreen.xib in Resources */ = {isa = PBXBuildFile; fileRef = 13B07FB11A68108700A75B9A /* LaunchScreen.xib */; };
 		13B07FBF1A68108700A75B9A /* Assets.xcassets in Resources */ = {isa = PBXBuildFile; fileRef = 13B07FB51A68108700A75B9A /* Assets.xcassets */; };
 		13B07FC11A68108700A75B9A /* main.m in Sources */ = {isa = PBXBuildFile; fileRef = 13B07FB71A68108700A75B9A /* main.m */; };
 		42689E9C23466FF7007540AA /* webview in Resources */ = {isa = PBXBuildFile; fileRef = 42689E9B23466FF7007540AA /* webview */; };
+		8BE55043253A2B6600B0BC8A /* LaunchScreen.storyboard in Resources */ = {isa = PBXBuildFile; fileRef = 8BE55041253A2B6600B0BC8A /* LaunchScreen.storyboard */; };
 		8BEA1EF024A6983D00674040 /* ZLPConstants.m in Sources */ = {isa = PBXBuildFile; fileRef = 8BEA1EEE24A6983D00674040 /* ZLPConstants.m */; };
 		A148FEFC1E9D8CB900479280 /* zulip.mp3 in Resources */ = {isa = PBXBuildFile; fileRef = A148FEFB1E9D8CB900479280 /* zulip.mp3 */; };
 		C091D09FD11FDDB8E939257D /* libPods-ZulipMobile.a in Frameworks */ = {isa = PBXBuildFile; fileRef = 74F3CD22CB932FA7EEE0BB66 /* libPods-ZulipMobile.a */; };
@@ -24,7 +24,6 @@
 		13B07F961A680F5B00A75B9A /* ZulipMobile.app */ = {isa = PBXFileReference; explicitFileType = wrapper.application; includeInIndex = 0; path = ZulipMobile.app; sourceTree = BUILT_PRODUCTS_DIR; };
 		13B07FAF1A68108700A75B9A /* AppDelegate.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; name = AppDelegate.h; path = ZulipMobile/AppDelegate.h; sourceTree = "<group>"; };
 		13B07FB01A68108700A75B9A /* AppDelegate.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; name = AppDelegate.m; path = ZulipMobile/AppDelegate.m; sourceTree = "<group>"; };
-		13B07FB21A68108700A75B9A /* Base */ = {isa = PBXFileReference; lastKnownFileType = file.xib; name = Base; path = Base.lproj/LaunchScreen.xib; sourceTree = "<group>"; };
 		13B07FB51A68108700A75B9A /* Assets.xcassets */ = {isa = PBXFileReference; lastKnownFileType = folder.assetcatalog; name = Assets.xcassets; path = ZulipMobile/Assets.xcassets; sourceTree = "<group>"; };
 		13B07FB61A68108700A75B9A /* Info.plist */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = text.plist.xml; name = Info.plist; path = ZulipMobile/Info.plist; sourceTree = "<group>"; };
 		13B07FB71A68108700A75B9A /* main.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; name = main.m; path = ZulipMobile/main.m; sourceTree = "<group>"; };
@@ -33,6 +32,7 @@
 		42689E9B23466FF7007540AA /* webview */ = {isa = PBXFileReference; lastKnownFileType = folder; path = webview; sourceTree = "<group>"; };
 		66E34CC6219226D10091B852 /* ZulipMobile-Bridging-Header.h */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.h; path = "ZulipMobile-Bridging-Header.h"; sourceTree = "<group>"; };
 		74F3CD22CB932FA7EEE0BB66 /* libPods-ZulipMobile.a */ = {isa = PBXFileReference; explicitFileType = archive.ar; includeInIndex = 0; path = "libPods-ZulipMobile.a"; sourceTree = BUILT_PRODUCTS_DIR; };
+		8BE55042253A2B6600B0BC8A /* Base */ = {isa = PBXFileReference; lastKnownFileType = file.storyboard; name = Base; path = ZulipMobile/Base.lproj/LaunchScreen.storyboard; sourceTree = "<group>"; };
 		8BEA1EEE24A6983D00674040 /* ZLPConstants.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; name = ZLPConstants.m; path = ZulipMobile/ZLPConstants.m; sourceTree = "<group>"; };
 		8BEA1EEF24A6983D00674040 /* ZLPConstants.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; name = ZLPConstants.h; path = ZulipMobile/ZLPConstants.h; sourceTree = "<group>"; };
 		A148FEFB1E9D8CB900479280 /* zulip.mp3 */ = {isa = PBXFileReference; lastKnownFileType = audio.mp3; path = zulip.mp3; sourceTree = "<group>"; };
@@ -67,11 +67,11 @@
 				13B07FB01A68108700A75B9A /* AppDelegate.m */,
 				13B07FB51A68108700A75B9A /* Assets.xcassets */,
 				13B07FB61A68108700A75B9A /* Info.plist */,
-				13B07FB11A68108700A75B9A /* LaunchScreen.xib */,
 				13B07FB71A68108700A75B9A /* main.m */,
 				CFA67D1F1EC23BCB0070048E /* UtilManager.m */,
 				CFA67D211EC23BDD0070048E /* UtilManager.h */,
 				66E34CC6219226D10091B852 /* ZulipMobile-Bridging-Header.h */,
+				8BE55041253A2B6600B0BC8A /* LaunchScreen.storyboard */,
 			);
 			name = ZulipMobile;
 			sourceTree = "<group>";
@@ -215,8 +215,8 @@
 			files = (
 				42689E9C23466FF7007540AA /* webview in Resources */,
 				13B07FBF1A68108700A75B9A /* Assets.xcassets in Resources */,
-				13B07FBD1A68108700A75B9A /* LaunchScreen.xib in Resources */,
 				A148FEFC1E9D8CB900479280 /* zulip.mp3 in Resources */,
+				8BE55043253A2B6600B0BC8A /* LaunchScreen.storyboard in Resources */,
 			);
 			runOnlyForDeploymentPostprocessing = 0;
 		};
@@ -370,13 +370,12 @@
 /* End PBXSourcesBuildPhase section */
 
 /* Begin PBXVariantGroup section */
-		13B07FB11A68108700A75B9A /* LaunchScreen.xib */ = {
+		8BE55041253A2B6600B0BC8A /* LaunchScreen.storyboard */ = {
 			isa = PBXVariantGroup;
 			children = (
-				13B07FB21A68108700A75B9A /* Base */,
+				8BE55042253A2B6600B0BC8A /* Base */,
 			);
-			name = LaunchScreen.xib;
-			path = ZulipMobile;
+			name = LaunchScreen.storyboard;
 			sourceTree = "<group>";
 		};
 /* End PBXVariantGroup section */

ios/ZulipMobile/Base.lproj/LaunchScreen.storyboard

@@ -0,0 +1,33 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<document type="com.apple.InterfaceBuilder3.CocoaTouch.Storyboard.XIB" version="3.0" toolsVersion="17156" targetRuntime="iOS.CocoaTouch" propertyAccessControl="none" useAutolayout="YES" launchScreen="YES" useTraitCollections="YES" useSafeAreas="YES" colorMatched="YES" initialViewController="01J-lp-oVM">
+    <device id="retina4_7" orientation="portrait" appearance="light"/>
+    <dependencies>
+        <deployment identifier="iOS"/>
+        <plugIn identifier="com.apple.InterfaceBuilder.IBCocoaTouchPlugin" version="17126"/>
+        <capability name="Named colors" minToolsVersion="9.0"/>
+        <capability name="Safe area layout guides" minToolsVersion="9.0"/>
+        <capability name="documents saved in the Xcode 8 format" minToolsVersion="8.0"/>
+    </dependencies>
+    <scenes>
+        <!--View Controller-->
+        <scene sceneID="EHf-IW-A2E">
+            <objects>
+                <viewController storyboardIdentifier="LaunchScreenViewController" id="01J-lp-oVM" sceneMemberID="viewController">
+                    <view key="view" contentMode="scaleToFill" id="2Zo-eZ-ckx">
+                        <rect key="frame" x="0.0" y="0.0" width="375" height="667"/>
+                        <autoresizingMask key="autoresizingMask" flexibleMaxX="YES" flexibleMaxY="YES"/>
+                        <viewLayoutGuide key="safeArea" id="yBM-Xp-f8I"/>
+                        <color key="backgroundColor" name="Brand"/>
+                    </view>
+                </viewController>
+                <placeholder placeholderIdentifier="IBFirstResponder" id="iYj-Kq-Ea1" userLabel="First Responder" sceneMemberID="firstResponder"/>
+            </objects>
+            <point key="canvasLocation" x="52.173913043478265" y="375"/>
+        </scene>
+    </scenes>
+    <resources>
+        <namedColor name="Brand">
+            <color red="0.31764705882352939" green="0.76078431372549016" blue="0.68627450980392157" alpha="1" colorSpace="custom" customColorSpace="sRGB"/>
+        </namedColor>
+    </resources>
+</document>