LibJS: Implement console.assert()

Author: https://github.com/linusg
Commit: 8d490aba76
Pull-request: https://github.com/SerenityOS/serenity/pull/6454
Reviewed-by: https://github.com/alimpfard

Userland/Services/WebContent/WebContentConsoleClient.h

@@ -56,6 +56,7 @@ private:
     virtual JS::Value trace() override;
     virtual JS::Value count() override;
     virtual JS::Value count_reset() override;
+    virtual JS::Value assert_() override;
 
     ClientConnection& m_client;
     WeakPtr<JS::Interpreter> m_interpreter;