feat: Implement mouse select chat list items

lib/components/mouse_over_builder.dart

@@ -0,0 +1,28 @@
+import 'package:flutter/material.dart';
+
+class MouseOverBuilder extends StatefulWidget {
+  final Function(BuildContext, bool) builder;
+
+  const MouseOverBuilder({Key key, this.builder}) : super(key: key);
+  @override
+  _MouseOverBuilderState createState() => _MouseOverBuilderState();
+}
+
+class _MouseOverBuilderState extends State<MouseOverBuilder> {
+  bool _hover = false;
+
+  void _toggleHover(bool hover) {
+    if (_hover != hover) {
+      setState(() => _hover = hover);
+    }
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    return MouseRegion(
+      onEnter: (_) => _toggleHover(true),
+      onExit: (_) => _toggleHover(false),
+      child: widget.builder != null ? widget.builder(context, _hover) : null,
+    );
+  }
+}