Add initial configuration, tokens, and widgets for M3E components

- Introduced `.gitignore` and `.metadata` for apps and examples.
- Added Flutter/Dart analysis configurations (`analysis_options.yaml`).
- Implemented foundational tokens and themes for M3E (colors, shapes).
- Created base implementations for `IconButtonM3E` and `SplitButtonM3E`.
- Set up CI workflow (`ci.yaml`) to automate testing and analysis.

packages/icon_button_m3e/example/pubspec.yaml

@@ -0,0 +1,21 @@
+name: icon_button_m3e_example
+description: Example for icon_button_m3e
+publish_to: "none"
+
+environment:
+  sdk: ">=3.2.0 <4.0.0"
+  flutter: ">=3.19.0"
+
+dependencies:
+  flutter:
+    sdk: flutter
+  icon_button_m3e:
+    path: ../
+
+dev_dependencies:
+  flutter_test:
+    sdk: flutter
+  flutter_lints: ^4.0.0
+
+flutter:
+  uses-material-design: true