Add GitHub community files

- CONTRIBUTING.md with blueprint submission guidelines
- Issue templates for bugs and feature requests
- Pull request template

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

.github/PULL_REQUEST_TEMPLATE.md

@@ -0,0 +1,24 @@
+## Description
+
+Brief description of the changes.
+
+## Type of Change
+
+- [ ] New blueprint
+- [ ] Bug fix
+- [ ] Enhancement to existing blueprint
+- [ ] Documentation update
+
+## Blueprint(s) Affected
+
+List the blueprints added or modified.
+
+## Testing
+
+Describe how you tested these changes in Home Assistant.
+
+## Checklist
+
+- [ ] Blueprint tested in Home Assistant
+- [ ] README.md updated (if adding new blueprint)
+- [ ] Blueprint includes proper metadata (name, description, domain)