Add support for Massdrop x Zslane Mercury Rocketeer

[jimelrod]

Per the QMK Docs, I'm requesting firmware to be available for the Massdrop x Zslane Mercury Rocketeer.

Cheers!

[drashna]

Well, massdrop has it in their repo, but it doesn't look like it's done?

https://github.com/Massdrop/qmk_firmware/tree/master/keyboards/massdrop/rocketeer

[tofagerl]

~~I can't make heads or tails of the Massdrop rocketeer folder. It looks like it's really just support files for use with their web configurator, which I don't want to use since I already have a QMK keymap I use with other keyboards. There's not even a Makefile there.

I don't usually do C. Had this been a Java project I might have known what to do to put together the missing pieces, but as it is I'm useless, and so is this keyboard.~~

Turns out it's more than possible that I just haven't used QMK in so long that I just don't recognize how QMK is laid out - I might get it working after all, which would be a nice surprise.

[drashna]

Well, a PR is opened, so hopefully, it will get merged in soon.