Refine .gitignore organization

Improve .gitignore organization for better clarity:

- Group negation patterns under "Allow specific files" comment

This improves readability and consistency with other socket-* repos.

Author: jdalton

.gitignore

@@ -16,4 +16,5 @@ Thumbs.db
 **/*.tsbuildinfo
 /dist
 
+# Allow specific files
 !/.vscode/extensions.json