Update README.md

Author: wisammechano

module4-authentication-and-security/README.md

@@ -24,4 +24,6 @@ A learning journey through implementation of authentication and authorization in
 
 2 [Auth Schemes [R]](./r2-auth-schemes/README.md)
 
-3 [Attack Trajectories and mitigation [R]](./r3-attack-trajectories-and-mitigation/README.md)
+3 [Attack Trajectories and mitigation [R]](./r3-attack-trajectories-and-mitigation/README.md)
+
+4 [Awesome Todos [L]](./r4-awesome-todos-lab/README.md)