Add issue template and other fixes

Author: mosuem

.github/ISSUE_TEMPLATE/source_maps.md

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

pkgs/source_maps/pubspec.yaml

@@ -1,7 +1,7 @@
 name: source_maps
 version: 0.10.13-wip
 description: A library to programmatically manipulate source map files.
-repository: https://github.com/dart-lang/source_maps
+repository: https://github.com/dart-lang/tools/tree/main/pkgs/source_maps
 
 environment:
   sdk: ^3.3.0