add contributing guide

Author: DivineDominion

CONTRIBUTING.md

@@ -0,0 +1,9 @@
+# Contributing to the Typewriter Modes project
+
+You're very welcome to suggest, change, adapt, and replace anything you like in a pull request! If you want to propose a dramatic change, please open an issue first for discussion before making a pull request, though. Because discussions in PRs often get messy easily.
+
+That being said, the usual guidelines apply:
+
+* fork this repository, 
+* commit changes to a new branch in your fork,
+* create a pull request from your branch to this repository's `master`.

README.md

@@ -52,6 +52,12 @@ I explain the parts in blog posts instead of making the readme even longer:
 * [Overscrolling](http://cleancocoa.com/posts/2017/07/typewriter-mode-overscrolling/)
 
 
+## Contributing
+
+There's still work to do to make all typewriter modes a pleasant experience. I'd love to see you involved! 
+
+For technical details, have a look at the [Contributing Guide](/CONTRIBUTING.md).
+
 ## License
 
 Copyright (c) 2017 Christian Tietze. Distributed under the MIT License.

Typewriter.xcodeproj/project.pbxproj

@@ -21,6 +21,9 @@
 /* End PBXBuildFile section */
 
 /* Begin PBXFileReference section */
+		507C47FC1F189D13009D43E3 /* LICENSE */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = text; path = LICENSE; sourceTree = "<group>"; };
+		507C47FD1F189D13009D43E3 /* README.md */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = net.daringfireball.markdown; path = README.md; sourceTree = "<group>"; };
+		507C48001F189F38009D43E3 /* CONTRIBUTING.md */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = net.daringfireball.markdown; path = CONTRIBUTING.md; sourceTree = "<group>"; };
 		5086C1BE1F15FAEA007A2D75 /* TypewriterMode.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = TypewriterMode.swift; sourceTree = "<group>"; };
 		5086C1C01F15FB05007A2D75 /* BottomOverscrollFlexibleTypewriterMode.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = BottomOverscrollFlexibleTypewriterMode.swift; sourceTree = "<group>"; };
 		5086C1C21F15FBC0007A2D75 /* FullOverscrollFlexibleTypewriterMode.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = FullOverscrollFlexibleTypewriterMode.swift; sourceTree = "<group>"; };
@@ -50,6 +53,9 @@
 		50CBA4731F0A35760092E8ED = {
 			isa = PBXGroup;
 			children = (
+				507C47FD1F189D13009D43E3 /* README.md */,
+				507C48001F189F38009D43E3 /* CONTRIBUTING.md */,
+				507C47FC1F189D13009D43E3 /* LICENSE */,
 				50CBA47E1F0A35760092E8ED /* Typewriter */,
 				50CBA47D1F0A35760092E8ED /* Products */,
 			);