Added better documentation to find the pub package (flutter#3)

Added better documentation to find the pub package on pub.dev

Author: vanlooverenkoen

third_party/packages/cupertino_icons/README.md

@@ -3,6 +3,18 @@
 This is an asset repo containing the default set of icon assets used by
 Flutter's [Cupertino widgets](https://github.com/flutter/flutter/tree/master/packages/flutter/lib/src/cupertino).
 
+# Usage
+
+https://pub.dev/packages/cupertino_icons
+
+[![pub package](https://img.shields.io/pub/v/cupertino_icons.svg)](https://pub.dev/packages/cupertino_icons)
+
+```
+dependencies:
+  cupertino_icons: ^<latest-version>
+```
+  
+
 # Issues
 
 For issues, file directly in the [main Flutter repo](https://github.com/flutter/flutter).