Add issue template and other fixes

Author: mosuem

.github/ISSUE_TEMPLATE/yaml.md

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

pkgs/yaml/pubspec.yaml

@@ -1,7 +1,7 @@
 name: yaml
 version: 3.1.3-wip
 description: A parser for YAML, a human-friendly data serialization standard
-repository: https://github.com/dart-lang/yaml
+repository: https://github.com/dart-lang/tools/tree/main/pkgs/yaml
 topics:
  - yaml
  - config-format