Create GitHub community/discussion starter content

[httpdss]

Summary

Prepare GitHub Discussions and community-facing content so new visitors have a clear place to ask questions, share templates, and contribute.

Scope

• Add or update issue/discussion templates if supported by the repo.
• Create suggested pinned Discussion topics:
  • Show us what you built with StructKit
  • Roadmap and ideas
  • Help wanted / good first contributions
  • Template requests
• Update CONTRIBUTING docs to point contributors to the right discussion/issue path.
• Add README links to Discussions and contribution entry points.

Acceptance criteria

• New users can easily find where to ask questions or share use cases.
• Contribution docs explain how to propose templates/examples.
• README points to Discussions and good-first contribution guidance.
• Templates reduce ambiguity when opening issues or discussions.