chore: update gitignore for Jekyll and test artifacts

- Add .jekyll-metadata (Jekyll incremental build cache)
- Add .playwright-mcp/ (test screenshot directory)
- Prevent temporary files from being tracked in repository

Author: JesperDramsch

.gitignore

@@ -5,6 +5,8 @@ vendor
 .DS_Store
 .idea
 .tmp
+.jekyll-metadata
+.playwright-mcp/
 
 # Byte-compiled / optimized / DLL files
 __pycache__/