Initial SAMD & Dygma Raise support

[algernon]

This adds the samd architecture to the Bundle, along with Dygma's Raise keyboard.

A couple of things I'm not 100% happy with:

• samd is a full Arduino Core, unlike avr which is based on top of ArduinoCore-avr. We should likely do the same for samd, but there are a number of local modifications to the core which I need to iron out first.
• samd/libraries/Wire is included as-is. We should ideally either submodule it, or use the base Core's library, or just get rid of it alltogether.
• samd/libraries/FlashStorage currently points to a repo owned by Dygma, while all other submodules we use are under keyboardio.
• samd/platform.txt currently sets the platform name to Dygma Keyboards
• To compile the Raise firmware, we need to symlink dygma to keyboardio in the Arduino Hardware directory, because the Raise firmware wants dygma:raise_native as FQBN.

The last two, I'm not sure how to resolve, and I do not think there's a good solution apart from having separate bundles.

[obra]

I'm looking at doing something similar, but starting from Adafruit's SAMD core, as it contains support for the SAMD51 mcus, which are more likely to be the ones we'd want to use.

[algernon]

Closing this as obsolete, Dymga went with their own bundle.