Add TRRS jack short protection / backpower protection

[JellyTitan]

Adding a DMG2305UX PFET to the left-hand side by the TRRS jack seems like a low-cost / low effort option for folks who want added backpower protection. Its a bog-standard SOT23 package, pretty easy for anyone comfortable with surface mount soldering, and the bypass option is just another simple solder-bridge.

Originally posted by @TheWerle in https://github.com/JellyTitan/Sofle-Pico/discussions/11#discussioncomment-8481411

Adding TRRS short protection would be really helpful! I don't have the bandwidth for this improvement right now, but I'd love to see this implemented. A through-hole alternative component would also be really nice, since this board may be the first/only soldering experience that many users have.