Refactor button component and add new sections for loading indicators, icons, and navigation; update enums and pubspec description

packages/button_m3e/README.md

@@ -1,70 +1,7 @@
+
 # button_m3e
 
-Material 3 **Expressive** Buttons for Flutter, built on top of Flutter's buttons but styled via **M3E** tokens.
+Material 3 **Expressive Buttons** for Flutter — sizes XS→XL, round/square shapes,
+toggle selection, and 5 styles (filled/tonal/elevated/outlined/text).
 
-Variants: **filled**, **tonal**, **outlined**, **text**, **elevated**  
-Sizes: **small**, **medium**, **large**  
-Shape families: **round**, **square**  
-Density: **regular**, **compact**
-
-> Depends on `m3e_design` (ThemeExtension with colors/typography/spacing/shapes).
-
-## Monorepo Layout
-
-```
-packages/
-  m3e_design/
-  button_m3e/
-```
-
-In `pubspec.yaml` this package references `../m3e_design`.
-
-## Usage
-
-```dart
-import 'package:button_m3e/button_m3e.dart';
-
-ButtonM3E(
-  variant: ButtonM3EVariant.filled,
-  size: ButtonM3ESize.medium,
-  labelText: 'Continue',
-  leading: const Icon(Icons.arrow_forward),
-  onPressed: () {},
-);
-```
-
-Full-width button:
-
-```dart
-const ButtonM3E(
-  variant: ButtonM3EVariant.tonal,
-  size: ButtonM3ESize.large,
-  labelText: 'Buy now',
-  expand: true,
-);
-```
-
-Outlined/Text/Elevated work similarly.
-
-## Theming via `m3e_design`
-
-`button_m3e` reads tokens from your theme:
-
-- `m3e.colors.*` for background/foreground/border/disabled
-- `m3e.type.labelLarge` for the button label
-- `m3e.shapes.round|square` (uses `.lg` radius for buttons)
-- `m3e.spacing` for horizontal paddings (`sm`, `md`, `lg`)
-
-If the extension is not present, it falls back to `M3ETheme.defaults(ColorScheme)`.  
-You can still override `ThemeData.colorScheme` to influence defaults globally.
-
-## Notes
-
-- Label can be provided as `labelText` (String) or `label` (Widget).
-- `leading`/`trailing` are optional helpers for icons.
-- `expand: true` makes the button take full width.
-- `density: compact` slightly reduces height for each size.
-
-## License
-
-MIT
+See `lib/src/button_tokens_adapter.dart` for measurements & color mapping.