Update README.md

Author: vandadnp

README.md

@@ -1,5 +1,6 @@
 # Table of Contents
 
+* [CompactMap on Map in Dart](tipsandtricks/compactmap-on-map-in-dart/compactmap-on-map-in-dart.md)
 * [iOS Context Menu in Flutter](tipsandtricks/ios-context-menu-in-flutter/ios-context-menu-in-flutter.md)
 * [Recursive Flatten of List in Dart](tipsandtricks/recursive-flatten-of-list-in-dart/recursive-flatten-of-list-in-dart.md)
 * [Async API Cleanup in Flutter](tipsandtricks/async-api-cleanup-in-flutter/async-api-cleanup-in-flutter.md)