LibJS: Implement Proxy.revocable()

Author: https://github.com/linusg
Commit: 9b35231453
Pull-request: https://github.com/SerenityOS/serenity/pull/7926

Userland/Libraries/LibJS/Runtime/ProxyConstructor.h

@@ -1,5 +1,6 @@
 /*
  * Copyright (c) 2020, Matthew Olsson <mattco@serenityos.org>
+ * Copyright (c) 2021, Linus Groh <linusg@serenityos.org>
  *
  * SPDX-License-Identifier: BSD-2-Clause
  */
@@ -23,6 +24,8 @@ public:
 
 private:
     virtual bool has_constructor() const override { return true; }
+
+    JS_DECLARE_NATIVE_FUNCTION(revocable);
 };
 
 }