Add automated marketplace publishing

[ensui-dev]

Summary

Adds automated publishing to VSCode Marketplace via GitHub Actions.

Changes

Automated Publishing Workflow

• New workflow: .github/workflows/publish.yml
• Triggers on git tags matching v* pattern
• Automatically builds, packages, and publishes extension
• Creates GitHub releases with auto-generated notes
• Uploads .vsix files as release artifacts

Package.json Enhancements

• Keywords: Added for marketplace discoverability (42, header, 42network, etc.)
• Categories: Added 'Formatters' category
• Gallery Banner: Dark theme configuration for marketplace page

How to Use

Create a new release with one command:

# 1. Update version in package.json and CHANGELOG.md
# 2. Commit and push changes
# 3. Create and push tag
git tag v0.42.11
git push origin v0.42.11

The workflow will automatically:

1. ✅ Build the extension
2. ✅ Publish to marketplace
3. ✅ Create GitHub release
4. ✅ Attach .vsix file

Prerequisites

• VSCODE_MARKETPLACE_TOKEN secret configured ✅ (already done)

Testing

• Workflow validated
• Package.json builds successfully
• Ready for first release

Documentation

Complete release process documented in RELEASE_GUIDE.md (gitignored)