Add Adafruit M0 Feather with GPS Featherwing example

[AmedeeBulle]

Added Adafruit M0 with GPS example as a submodule so it links to the original repo rather than duplicating everything -- if this is OK with you.

[jpmeijers]

I guess submodules is an option, but for the other examples I just added a README.md with a description and hyperlink to the actual repo. That allows users to browse github and go to the appropriate repo without having to clone this one. It also allows to have a list of multiple examples for the same hardware platform.

How does github handle submodules? Will it send users browsing this repo to the actual one so that they end up cloning only the one they need?

[AmedeeBulle]

Seems that GH makes a link -- see https://github.com/AmedeeBulle/gps-node-examples

I am happy with whatever you prefer, I can align on what you already have -- somehow I missed the Pycom example...

(Links might actually be better, as submodules link to specific commit)