feat: add extensions for creating AnimationSpec and Duration

packages/fleet/example/lib/simple_declerative_animation.dart

@@ -33,7 +33,7 @@ class _MyHomePageState extends State<MyHomePage> {
     return Scaffold(
       body: Center(
         child: Animated(
-          animation: AnimationSpec.ease(const Duration(seconds: 1)),
+          animation: AnimationSpec.ease(1.s),
           value: _expanded,
           child: ASizedBox.fromSize(
             size: _expanded ? const Size.square(400) : const Size.square(200),

packages/fleet/example/lib/simple_imperative_animation.dart

@@ -41,13 +41,10 @@ class _MyHomePageState extends State<MyHomePage> {
   }
 
   void _expand() {
-    setStateWithAnimation(
-      AnimationSpec.curve(Curves.easeInOutExpo, const Duration(seconds: 1)),
-      () {
-        _color = _expandedColor;
-        _size = (context.findRenderObject()! as RenderBox).size;
-      },
-    );
+    setStateWithAnimation(AnimationSpec.curve(Curves.easeInOutExpo, 1.s), () {
+      _color = _expandedColor;
+      _size = (context.findRenderObject()! as RenderBox).size;
+    });
   }
 
   @override

packages/fleet/example/lib/stack.dart

@@ -52,11 +52,8 @@ class StackElement extends StatelessWidget {
   final bool left;
 
   AnimationSpec _buildAnimation() {
-    return AnimationSpec.curve(
-      Curves.easeInOutCubic,
-      const Duration(milliseconds: 500) -
-          const Duration(milliseconds: 25) * index,
-    ).delay(const Duration(milliseconds: 50) * index);
+    return AnimationSpec.curve(Curves.easeInOutCubic, 500.ms - 25.ms * index)
+        .delay(50.ms * index);
   }
 
   Color _buildColor() =>

packages/fleet/lib/fleet.dart

@@ -27,4 +27,5 @@ export 'src/animatable_widgets.dart'
     show AAlign, AColoredBox, AContainer, ASizedBox;
 export 'src/animate.dart'
     show Animated, FleetBinding, withAnimation, SetStateWithAnimationExtension;
-export 'src/animation.dart' show AnimationSpec;
+export 'src/animation.dart' show AnimationSpec, AnimationFromCurveExtension;
+export 'src/duration.dart' show DurationFromIntExtension;

packages/fleet/lib/src/animation.dart

@@ -165,6 +165,22 @@ class AnimationSpec with Diagnosticable {
       _speed.hashCode;
 }
 
+/// Extension for creating [AnimationSpec]s from [Curve]s.
+///
+/// See also:
+///
+/// - [AnimationSpec.curve]
+extension AnimationFromCurveExtension on Curve {
+  /// Creates an [AnimationSpec] which uses this [Curve].
+  ///
+  /// See also:
+  ///
+  /// - [AnimationSpec.curve]
+  AnimationSpec animation([Duration duration = AnimationSpec.defaultDuration]) {
+    return AnimationSpec.curve(this, duration);
+  }
+}
+
 /// The current [AnimationSpec] that will be used to animated visual changes.
 AnimationSpec? get currentAnimation => _currentAnimation;
 AnimationSpec? _currentAnimation;

packages/fleet/lib/src/duration.dart

@@ -0,0 +1,20 @@
+/// Extension for creating [Duration]s from [int]s.
+extension DurationFromIntExtension on int {
+  /// A [Duration] that is as many **days** long as this value.
+  Duration get d => Duration(days: this);
+
+  /// A [Duration] that is as many **hours** long as this value.
+  Duration get h => Duration(hours: this);
+
+  /// A [Duration] that is as many **minutes** long as this value.
+  Duration get m => Duration(minutes: this);
+
+  /// A [Duration] that is as many **seconds** long as this value.
+  Duration get s => Duration(seconds: this);
+
+  /// A [Duration] that is as many **milliseconds** long as this value.
+  Duration get ms => Duration(milliseconds: this);
+
+  /// A [Duration] that is as many **microseconds** long as this value.
+  Duration get us => Duration(microseconds: this);
+}