Feature Request: Add additional RAM to Sprig

[polypixeldev]

The 264kb of RAM on the RP2040 works well for most things but isn't enough for more complex tasks or non-optimal code. Adding more RAM would make modding Spade and other software for the Sprig much easier and feasible.

To do this, PSRAM can be connected over SPI and accessed in software using https://github.com/polpo/rp2040-psram.