tip for using sudo !! to repeat previous command with sudo

This PR adds a new tip explaining how to use sudo !! to re-run the last command with superuser privileges. This is a commonly used and very practical command-line trick, especially helpful when a user forgets to prepend a command with sudo. Example use case: apt update # returns permission denied sudo !! # re-runs as: sudo apt update This addition aligns with the spirit of the repository, helping users master small but powerful command-line techniques. Let me know if any revisions are needed. Happy to update!