Support for Adafruit Feather RP2040 "Adalogger" board?

[b4shful]

https://www.adafruit.com/product/5980

Recently picked up this board, and then realised that the documentation only mentions using it with CircuitPython/MicroPython or earlephilhower RP2040 Arduino core.

Not sure if this is trivial/just a matter of adding a header, or if it would take a lot more work to properly support this board and use it with Pico SDK.

I am aware that using some of the peripherals on the board like the microSD would be more involved and probably up to the user to implement, but I guess the pin definitions etc. would be nice at least so that basic functionality is possible with Pico SDK without needing any tweaks or using other abstraction layers.

[b4shful]

Took a crack at it myself, see #2524

[lurch]

PR merged into develop