Add issue template and other fixes

Author: mosuem

.github/ISSUE_TEMPLATE/typed_data.md

@@ -0,0 +1,5 @@
+---
+name: "package:typed_data"
+about: "Create a bug or file a feature request against package:typed_data."
+labels: "package:typed_data"
+---

pkgs/typed_data/CONTRIBUTING.md

@@ -2,7 +2,7 @@ name: typed_data
 version: 1.4.0-wip
 description: >-
   Utility functions and classes related to the dart:typed_data library.
-repository: https://github.com/dart-lang/typed_data
+repository: https://github.com/dart-lang/core/tree/main/pkgs/typed_data
 
 topics:
   - data-structures