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/slider_m3e/README.md

@@ -0,0 +1,69 @@
+# slider_m3e
+
+Material 3 **Expressive** Sliders for Flutter. Single-value and range sliders, with token-driven colors, sizes, and shapes.
+
+- `SliderM3E` — single-value slider, optional start/end icons, discrete or continuous
+- `RangeSliderM3E` — range selection with the same styling
+- `sliderThemeM3E(...)` — generate a `SliderThemeData` from **M3E** tokens
+
+All styling reads the `M3ETheme` ThemeExtension from your `m3e_design` package.
+
+## Monorepo Layout
+
+```
+packages/
+  m3e_design/
+  slider_m3e/
+```
+
+`pubspec.yaml` references `../m3e_design`.
+
+## Usage
+
+```dart
+import 'package:slider_m3e/slider_m3e.dart';
+
+// Single slider
+SliderM3E(
+  value: 0.35,
+  onChanged: (v) {},
+  divisions: 10, // discrete
+  size: SliderM3ESize.large,
+  emphasis: SliderM3EEmphasis.primary,
+  shapeFamily: SliderM3EShapeFamily.round, // or square (expressive)
+  startIcon: const Icon(Icons.volume_mute),
+  endIcon: const Icon(Icons.volume_up),
+);
+
+// Range slider
+RangeSliderM3E(
+  values: const RangeValues(0.2, 0.8),
+  onChanged: (r) {},
+  divisions: 8,
+  size: SliderM3ESize.medium,
+  emphasis: SliderM3EEmphasis.secondary,
+  shapeFamily: SliderM3EShapeFamily.square,
+);
+```
+
+## Tokens mapping
+
+- **Colors:**
+  - Active: `primary` / `secondary` / `onSurface` (by emphasis)
+  - Inactive track: `onSurface` @ 24% opacity
+  - Overlay: active color @ 12% opacity
+  - Value indicator: `secondaryContainer` with `onSecondaryContainer` text
+- **Sizes:**
+  - Track height: small **≈2dp**, medium **≈4dp**, large **≈6dp**
+  - Thumb radius: small **≈10dp**, medium **≈12dp**, large **≈14dp**
+- **Density:** `compact` slightly reduces track and thumb sizes
+- **Shapes:** `round` uses round thumb, `square` uses a rounded-rect thumb for an expressive look
+
+## Accessibility
+
+- Set `semanticLabel` to announce values (percentage format by default).
+- Discrete sliders (with `divisions`) will show value indicators when `showValueIndicator` is enabled (or `onlyForDiscrete` by default).
+
+## License
+
+MIT