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.

pubspec.yaml

@@ -0,0 +1,8 @@
+name: m3e_workspace
+publish_to: 'none'
+
+environment:
+  sdk: ">=3.5.0 <4.0.0"
+
+dev_dependencies:
+  melos: ^6.1.0