docs(profile): add Contributing section with good-first-issue entry points

[ulises-jeremias]

Context

The Create-Python-App org profile README lists projects but lacks a Contributing section with entry points for newcomers (CNA's org profile is richer).

Steps

1. Read Create-Node-App/.github/profile/README.md for structure inspiration.
2. Add a Contributing section to CPA's org profile README.
3. Link each repo's CONTRIBUTING (where it exists), Discord, and a good first issue search.
4. Mention starter-friendly work types (docs, tests, README gaps) and that assigned AI/ML epic work should not be duplicated.

Acceptance criteria

• Contributing section present on org profile README
• Links to key repos + Discord invite https://discord.gg/bR5VyATgka
• Mentions good first issue label
• Notes not to pile onto already-assigned epics without coordinating

Files

• .github profile README (profile/README.md)

How to verify

Visit https://github.com/Create-Python-App and confirm the new section renders.