Add linked dart doc for Display on media query. (#139587)

FlutterView.display.size tells you the resolution of the display on supported platforms. FlutterView.physicalSize tells you the view size, which may be different from the display. This can help you tell if you are being letterboxed on android. 

https://medium.com/flutter/developing-flutter-apps-for-large-screens-53b7b0e17f10

Related to [flutter/website/9896](flutter/website#9896)

Author: reidbaker

packages/flutter/lib/src/widgets/media_query.dart

@@ -290,7 +290,8 @@ class MediaQueryData {
   ///
   /// See also:
   ///
-  /// * [FlutterView.physicalSize], which returns the size in physical pixels.
+  /// * [FlutterView.physicalSize], which returns the size of the view in physical pixels.
+  /// * [FlutterView.display], which returns reports display information like size, and refresh rate.
   /// * [MediaQuery.sizeOf], a method to find and depend on the size defined for
   ///   a [BuildContext].
   final Size size;