Document the converter example and community launch draft

[CrushOnAI]

Summary

• add a compact SillyTavern input-to-output walkthrough
• document the tested field mapping and safe defaults
• add a review-ready SillyTavern Show and tell draft
• link both resources from the repository README

Guardrails

• SFW fixtures only
• describes output as normalized structural JSON, not an official native CrushOn export
• does not claim complete compatibility
• community post remains a draft and has not been published

Verification

• PYTHONPATH=src python3 -m unittest discover -s tests -v (5 passed)
• git diff --check (passed)

Remaining before community publication

• add a current SFW screenshot after a successful live conversion
• final human review and explicit publication approval