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.

apps/gallery/pubspec_overrides.yaml

@@ -0,0 +1,30 @@
+# melos_managed_dependency_overrides: icon_button_m3e,m3e_collection,m3e_design,split_button_m3e,app_bar_m3e,button_group_m3e,button_m3e,fab_m3e,loading_indicator_m3e,navigation_bar_m3e,navigation_rail_m3e,progress_indicator_m3e,slider_m3e,toolbar_m3e
+dependency_overrides:
+  app_bar_m3e:
+    path: ..\\..\\packages\\app_bar_m3e
+  button_group_m3e:
+    path: ..\\..\\packages\\button_group_m3e
+  button_m3e:
+    path: ..\\..\\packages\\button_m3e
+  fab_m3e:
+    path: ..\\..\\packages\\fab_m3e
+  icon_button_m3e:
+    path: ..\\..\\packages\\icon_button_m3e
+  loading_indicator_m3e:
+    path: ..\\..\\packages\\loading_indicator_m3e
+  m3e_collection:
+    path: ..\\..\\packages\\m3e_collection
+  m3e_design:
+    path: ..\\..\\packages\\m3e_design
+  navigation_bar_m3e:
+    path: ..\\..\\packages\\navigation_bar_m3e
+  navigation_rail_m3e:
+    path: ..\\..\\packages\\navigation_rail_m3e
+  progress_indicator_m3e:
+    path: ..\\..\\packages\\progress_indicator_m3e
+  slider_m3e:
+    path: ..\\..\\packages\\slider_m3e
+  split_button_m3e:
+    path: ..\\..\\packages\\split_button_m3e
+  toolbar_m3e:
+    path: ..\\..\\packages\\toolbar_m3e