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/m3e_design/lib/tokens/shape_tokens.dart

@@ -0,0 +1,51 @@
+import 'package:flutter/material.dart';
+
+enum M3EShapeVariant { round, square }
+
+@immutable
+class M3EShapeSet {
+  final BorderRadius xs;
+  final BorderRadius sm;
+  final BorderRadius md;
+  final BorderRadius lg;
+  final BorderRadius xl;
+  const M3EShapeSet({required this.xs, required this.sm, required this.md, required this.lg, required this.xl});
+}
+
+@immutable
+class M3EShapes {
+  final M3EShapeSet round;
+  final M3EShapeSet square;
+
+  const M3EShapes({required this.round, required this.square});
+
+  factory M3EShapes.expressive() => const M3EShapes(
+        round: M3EShapeSet(
+          xs: BorderRadius.all(Radius.circular(999)),
+          sm: BorderRadius.all(Radius.circular(20)),
+          md: BorderRadius.all(Radius.circular(28)),
+          lg: BorderRadius.all(Radius.circular(44)),
+          xl: BorderRadius.all(Radius.circular(64)),
+        ),
+        square: M3EShapeSet(
+          xs: BorderRadius.all(Radius.circular(6)),
+          sm: BorderRadius.all(Radius.circular(8)),
+          md: BorderRadius.all(Radius.circular(12)),
+          lg: BorderRadius.all(Radius.circular(16)),
+          xl: BorderRadius.all(Radius.circular(20)),
+        ),
+      );
+
+  static M3EShapes lerp(M3EShapes a, M3EShapes b, double t) => M3EShapes(
+    round: _lerpSet(a.round, b.round, t),
+    square: _lerpSet(a.square, b.square, t),
+  );
+
+  static M3EShapeSet _lerpSet(M3EShapeSet a, M3EShapeSet b, double t) => M3EShapeSet(
+    xs: BorderRadius.lerp(a.xs, b.xs, t)!,
+    sm: BorderRadius.lerp(a.sm, b.sm, t)!,
+    md: BorderRadius.lerp(a.md, b.md, t)!,
+    lg: BorderRadius.lerp(a.lg, b.lg, t)!,
+    xl: BorderRadius.lerp(a.xl, b.xl, t)!,
+  );
+}