Add new board: Cytron Maker Zero SAMD21

[mlhakimz]

Hello, can you help to add this new board?

https://my.cytron.io/p-maker-zero-samd21

Thanks.

[dhalbert]

@mlhakimz There is apparently some extra white space in the pins.c file. Could you look at the "X" item in https://github.com/adafruit/circuitpython/runs/6589280392?check_suite_focus=true, and remove the whitespace. There is a diff in there showing which line. I would edit your PR but something is preventing that (normally there is a box you can check to allow it).

[mlhakimz]

@dhalbert Thanks for reviewing. I have deleted the white spaces you mentioned.

[dhalbert]

This is fine but one comment about the ordering of the pin names, if you want to change it.

[mlhakimz]

@dhalbert I'm keeping the pins order for now. Please merge the PR. Thanks again.