THV-0029: Skills Support in ToolHive Registry Server (MVP) (#29)

* Add RFC for Skills Support in ToolHive Registry Server (MVP)

Signed-off-by: Juan Antonio Osorio <ozz@stacklok.com>

* Address PR feedback: registry-scoped endpoints and flexible versioning

- Update diagram to show registry-scoped endpoint patterns
- Change version constraint from semver to any non-empty string
- Add note explaining version derivation from OCI tag/Git ref
- Make all API endpoints registry-scoped (/{regName}/v0.1/x/...)
- Document comma-separated IN filtering for status parameter

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

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Signed-off-by: Juan Antonio Osorio <ozz@stacklok.com>
Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>

Author: JAORMX