add swipe to reply

Fixes #90

lib/widgets/swipe_to_reply.dart

@@ -0,0 +1,58 @@
+import "package:flutter/services.dart";
+import "package:flutter_hooks/flutter_hooks.dart";
+import "package:material_ui/material_ui.dart";
+
+class const SwipeToReply(
+  final Widget child, {
+  required final VoidCallback? onSwipe,
+  super.key,
+}) extends HookWidget {
+  static const maxDrag = 64.0;
+  static const threshold = 0.75;
+
+  @override
+  Widget build(BuildContext context) {
+    final controller = useAnimationController(duration: Durations.short4);
+    useListenable(controller);
+
+    if (onSwipe == null) return child;
+
+    final progress = controller.value;
+
+    return GestureDetector(
+      onHorizontalDragUpdate: (details) {
+        final previous = controller.value;
+        controller.value = previous + details.primaryDelta! / maxDrag;
+
+        if (previous < threshold && controller.value >= threshold) {
+          HapticFeedback.lightImpact();
+        }
+      },
+      onHorizontalDragEnd: (_) {
+        if (controller.value >= threshold) onSwipe!();
+        controller.animateBack(0, curve: Curves.easeOut);
+      },
+      onHorizontalDragCancel: () =>
+          controller.animateBack(0, curve: Curves.easeOut),
+      child: Stack(
+        alignment: .centerLeft,
+        children: [
+          Positioned(
+            left: 16,
+            child: Opacity(
+              opacity: (progress / threshold).clamp(0, 1),
+              child: Transform.scale(
+                scale: progress >= threshold ? 1 : 0.75,
+                child: const Icon(Icons.reply),
+              ),
+            ),
+          ),
+          Transform.translate(
+            offset: .new(progress * maxDrag, 0),
+            child: child,
+          ),
+        ],
+      ),
+    );
+  }
+}