Release 2.1.0: sponsor button, GPT 5.5 model, resolver fixes

- Add Sponsor button via .github/FUNDING.yml and package.json sponsor field (GitHub Sponsors)
- Default GPT quick-model to mainline GPT 5.5 (was GPT 5.3 Codex)
- Retarget OpenAI resolver to gpt-<ver> / gpt-<ver>-mini slugs instead of -codex variants
- Fix non-existent gpt-5.5-mini fallback to gpt-5.4-mini
- Bump version to 2.1.0 and update CHANGELOG

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Add 2.0.4 and 2.0.6 release notes to CHANGELOG

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Bump version to 2.0.4

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Bump version to 1.1.0

- Update changelog with all new features since 1.0.7
- Add Inline Diff Viewer section to README
- Update package.json version

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

Add changelog

Fix permissions and add windows support

Update README.md

changelog

Create new release