chore: update .gitignore to include Android C++ build files

- Added `android/app/.cxx/` to ignore C++ build artifacts for Android.

Author: MoKamall

example/.gitignore

@@ -39,3 +39,6 @@ app.*.symbols
 
 # Obfuscation related
 app.*.map.json
+
+# Android related
+android/app/.cxx/