Add 5G-NB-IoT Board + Arduino Core Support

[maxgerhardt]

Closes #186.

Confirmed working in https://community.platformio.org/t/how-to-find-upload-protocol-for-this-samd21g18a-board/27231/13?u=maxgerhardt.

Notes:

• yes variant of arduino_zero is correct, they did not bother to changing the variant name
• "vendor": "Arduino LLC" instead of the more correct "5G HUB" is being used because that is the USB manufacturer and I wanted it to be equal with usb_manufacturer (though it would be nice to have a correct vendor metainfo and a new usb_manufacturer subfield)
• Please create a framework-arduino-samd-5gnbiot package in accordance to https://github.com/maxgerhardt/framework-arduino-samd-5gnbiot or the original link and upload it into the registry instead of using the git link

[torntrousers]

Hi, is there some problem thats holding up getting this merged and out in a release?

[torntrousers]

thanks for keeping this updated. i still don't understand why it can't just be merged.