Add p3a

Adds [p3a](https://github.com/fabkury/p3a), an open-source Wi-Fi pixel art player for the ESP32-P4. It displays animated WebP/GIF/PNG/JPEG and streams trending GIFs from Giphy as well as artworks from the Makapix Club pixel art social network. Runs on the Waveshare ESP32-P4-WIFI6-Touch-LCD-4B (720×720 IPS + GT911 touch + ESP32-C6 Wi-Fi 6 co-processor). Guideline checks: - ESP-related: yes — ESP-IDF firmware targeting the ESP32-P4. - Link works, HTTPS, no redirects.