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.

analysis_options.yaml

@@ -0,0 +1,11 @@
+linter:
+  rules:
+    always_declare_return_types: true
+    directives_ordering: true
+    prefer_single_quotes: true
+    sort_pub_dependencies: true
+
+analyzer:
+  exclude:
+    - "**/*.g.dart"
+    - "**/*.freezed.dart"