fix: include essential Control Panel JavaScript assets

- Add IconManagerField.js for field functionality
- Update .gitignore to allow plugin dist assets while excluding build artifacts
- Resolves 'file or directory to be published does not exist' error

Author: bhlindemann

.gitignore

@@ -22,12 +22,15 @@ yarn-error.log*
 .npm
 .yarn-integrity
 
-# Build outputs
-dist/
+# Build outputs (but keep plugin assets)
 build/
 *.min.js
 *.min.css
 
+# Exclude dist/ except for plugin assets
+dist/
+!src/web/assets/*/dist/
+
 # Logs
 logs
 *.log