feat(ui_kit): make flat button fade on transition

packages/wyatt_ui_kit/lib/src/components/buttons/flat_button/flat_button_screen.dart

@@ -130,9 +130,24 @@ class FlatButtonScreen extends CubitScreen<ButtonCubit, ButtonState> {
             onPressed?.call(state.state);
             bloc(context).onClickUpOut();
           },
-          child: DecoratedBox(
+          child: AnimatedContainer(
+            // TODO(wyatt): make it configurable, and generalize it
+            duration: const Duration(milliseconds: 150),
+            curve: Curves.easeOut,
             decoration: BoxDecoration(
               color: style.backgroundColors?.color,
+
+              // if no gradient colors => no default value
+              gradient: (style.backgroundColors?.isGradient ?? false)
+                  ? LinearGradient(
+                      colors: style.backgroundColors!.colors,
+                    )
+                  : null,
+
+              borderRadius: style.radius,
+            ),
+            child: DecoratedBox(
+              decoration: BoxDecoration(
                 // If no border color => no default value
                 border: (style.borderColors != null && style.stroke != null)
                     ? (style.borderColors?.isGradient ?? false)
@@ -147,12 +162,7 @@ class FlatButtonScreen extends CubitScreen<ButtonCubit, ButtonState> {
                             width: style.stroke!,
                           )
                     : null,
-              // if no gradient colors => no default value
+
-              gradient: (style.backgroundColors?.isGradient ?? false)
-                  ? LinearGradient(
-                      colors: style.backgroundColors!.colors,
-                    )
-                  : null,
                 boxShadow: [
                   if (style.shadow != null) ...[style.shadow!]
                 ],
@@ -245,6 +255,7 @@ class FlatButtonScreen extends CubitScreen<ButtonCubit, ButtonState> {
             ),
           ),
         ),
+      ),
     );
   }
 }