Make README include hardware instructions as well

[MDr164]

We should add some pictures and instructions on how to get the hardware up and running, including the pinout.

[Th3Fanbus]

+1, I was not sure which side I should solder the connectors for the RPi Pico to (all connectors go on the same side, and the picoprog uses the SPI pins of the Pico so you can use that as reference).