Create CONTRIBUTING.md and community governance docs #6

Summary

Create organization-level contributing guidelines and community governance documentation for the Azure Local org.

Deliverables

CONTRIBUTING.md (org-level, in github.io repo)

• How to contribute (issues, PRs, docs, code)
• Branch naming conventions
• Commit message format (conventional commits for release-please)
• PR review process
• Code of Conduct reference
• Development environment setup
• How to set up MkDocs locally for docs contributions
• Link to each repo's specific contributing guide

CODE_OF_CONDUCT.md

• Adopt Contributor Covenant or Microsoft Open Source CoC

Issue & PR Templates (org-wide)

• Bug report template
• Feature request template
• Documentation improvement template
• PR template with checklist

Why

As the org grows and potentially accepts community contributions, having clear guidelines reduces friction and sets expectations. Each solution repo's contributing.md currently links to a root CONTRIBUTING that doesn't exist or is minimal.