Update documentation to detail how to build this for rp2

[ril3y]

The esp32 documentation is the only one available on how to build the driver and micropython. Can you provide some instructions on building for rpi pico?

[flashypepo]

@ril3y: maybe next could help, if not already solved by you:

Issue following Terminal make command in folder micropython/ports/rp2:

$make -j LTO=1 BOARD=RPI_PICO USER_C_MODULES=../../../micropython_user_modules/st7789_mpy-master/st7789/micropython.cmake

By trial-and-error I discovered that the cmake file itself needs to be mentioned in the make command line not only the folder in which a cmake-file is placed.

PS.The folder micropython_user_modules is my custom folder where I place the user C modules.

In the Build-RPI_PICO folder look in the folder CMakeFiles where you can find deep in the folder firmware.dir the compiled st7789_mpy files.

Hope this is detailed enough. You can extract other command lines from the esp32 description.

Kind regards, Peter