Add issue template and other fixes

Author: mosuem

.github/ISSUE_TEMPLATE/stream_transform.md

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

pkgs/stream_transform/pubspec.yaml

@@ -1,7 +1,7 @@
 name: stream_transform
 version: 2.1.1-wip
 description: A collection of utilities to transform and manipulate streams.
-repository: https://github.com/dart-lang/stream_transform
+repository: https://github.com/dart-lang/tools/tree/main/pkgs/stream_transform
 
 environment:
   sdk: ^3.1.0