Add app testing and learn Flutter

.gitignore

@@ -23,4 +23,20 @@
 
 # Archivos de Android Studio
 **/*.jks
-**/*.keystore
+**/*.keystore
+
+# Flutter/Dart specific
+**/.dart_tool/
+**/.flutter-plugins
+**/.flutter-plugins-dependencies
+**/build/
+**/.dart_tool/
+**/.pub/
+**/.packages
+**/pubspec.lock
+
+# IDE files
+**/.vscode/
+
+# Windows
+**/Thumbs.db