Add keyboard Southpaw66

[gooberpsycho]

u/rpiguy9907 from reddit custom designed this PCB for their own personal use. I got a spare from them and decided to code up QMK and VIA support for it. They have released the schematics and Gerber files on their github available at :
https://github.com/rpiguy9907/Keyboards/tree/master/Southpaw66. It's basically a Clueboard/660 layout but with the mini-nav cluster and arrow keys on the left side instead of right.

Description

A few weeks ago, I coded firmware for a handwired clueboard named "3dp660". I basically just copied all the code from that, changing what needed to be changed. After a few hiccups, it compiled properly and I've tested it with the via json to ensure that it functions properly.

QMK Pull Request

qmk/qmk_firmware#10782

Checklist

• [x ] The QMK source code follows the guide here: https://caniusevia.com/docs/configuring_qmk
• [x ] The VIA definition follows the guide here: https://caniusevia.com/docs/layouts
• [x ] I have tested this keyboard definition using VIA's "Design" tab.
• [x ] I have tested this keyboard definition with firmware on a device.
• [x ] I have assigned alpha keys and modifier keys with the correct colors.
• The Vendor ID is not 0xFEED