[File] I have a patch for adding UF2 support

[Blake Ramsdell]

There is a standard in use for packaging firmware updates called UF2
that I have written a patch for. The file specification is here
https://github.com/microsoft/uf2 -- it's gaining popularity in the
Arduino / Raspberry Pi Pico / firmware community.

Didn't want to just send the patch if it's not appropriate. I believe
I have adhered to best practices, though my patch-fu will probably be
hampered by GMail. Thanks in advance.