add two new evasion techniques to the stealth plugin without external package import

lib/src/plugins/lib/random_user_agents.dart

@@ -0,0 +1,43 @@
+/// A dart library for generating random user agents.
+library random_user_agents;
+
+import 'dart:math';
+
+part 'user_agents.dart';
+
+/// Random UserAgents
+class RandomUserAgents {
+  /// a filtered list of user agents
+  final List<String> _list;
+
+  /// Creates a random number generator
+  final Random _random = Random();
+
+  /// Return an instance of RandomUserAgents using a private named constructor.
+  /// The instance is created with a filter function and a filtered list of user agents.
+  factory RandomUserAgents([bool Function(String value)? filter]) {
+    if (filter == null) {
+      return RandomUserAgents._internal(
+        _userAgents,
+      );
+    }
+
+    return RandomUserAgents._internal(
+      _userAgents.where(filter).toList(),
+    );
+  }
+
+  /// a private named constructor
+  RandomUserAgents._internal(this._list);
+
+  /// Return a random user agent string
+  static String random() {
+    Random random = Random();
+    return _userAgents[random.nextInt(_userAgents.length)];
+  }
+
+  /// Return a random user agent string
+  String getUserAgent() {
+    return _list[_random.nextInt(_list.length)];
+  }
+}