Martin on Nostr: Updated our Spanish language "Signal for beginners" and "locking down Signal" guides ...

Updated our Spanish language "Signal for beginners" and "locking down Signal" guides to include new changes to usernames. Check them out:
- https://freedom.press/training/signal-la-app-de-mensajeria-segura-guia-para-principiantes/
- https://freedom.press/training/proteccion-avanzada-para-signal/