Pro Micro support

[NoahAndrews]

We'd apparently need to bundle AVRDUDE. Here's a reference on how to use it with the Pro Micro.

[chief-wrench]

@NoahAndrews Can you give a coarse "when" estimate please? Do you need a Pro Micro for testing? I buy them for cheaps on AliExpress. And I'd send one or two to developers.

[NoahAndrews]

I've actually got a few coming. They're coming from China, so they could be here any time from the 20th to late next month.

As for the actual support itself, it's hard to say. It looks like the pro micros are a lot less "plug and play" to flash than other options, so I'm not even totally sure that it's going to be feasible to add support for them, and it make take a while if it is. I'll give it a fair shake though, probably starting pretty quickly after I receive them.

[NoahAndrews]

This library may be useful for us in querying the active serial ports. https://github.com/EmergingTechnologyAdvisors/node-serialport#electron

[jackhumbert]

It'd be nice if we could support alternate flashers (like -c avrisp) with avrdude as well, so we could recommend the QMK Flasher in the ISP flashing guide.