[Keyboard] Initial firmware and keymaps for the CO60 PCB (#5959)

* Add: Initial firmware and keymaps for the CO60 PCB

* Apply suggestions from code review

Co-Authored-By: noroadsleft <18669334+noroadsleft@users.noreply.github.com>
Co-Authored-By: Drashna Jaelre <drashna@live.com>
Co-Authored-By: fauxpark <fauxpark@gmail.com>

* Update: Address reviewer comments

* Apply suggestions from code review

Co-Authored-By: Drashna Jaelre <drashna@live.com>

* Update: Reviewer changes

keyboards/handwired/co60/readme.md

@@ -0,0 +1,26 @@
+# co60
+
+The CO60 is a 60% PCB that aims to meet the following goals:
+
+* Switches oriented such that the LEDs are South-facing, for
+  compatibility with Cherry profile keycaps.
+* USB Type-C support in both A to C and C to C configurations.
+* QMK support.
+* A variety of split spacebar configurations, including split 6.25U
+  space and split 7U space.
+* ESD protection circuitry, including data line protection and a
+  polyfuse on the VCC line.
+* Support for per-switch LED backlighting.
+* Fits in standard 60% keyboard cases.
+
+More info on the project, including all of the design files, can be found [here](https://github.com/jmdaly/CO60).
+
+Keyboard Maintainer: [jmdaly](https://github.com/jmdaly)  
+Hardware Supported: Supports the CO60 PCB rev1, rev6, rev7  
+Hardware Availability: Through group buys.
+
+Make example for this keyboard (after setting up your build environment):
+
+    make handwired/co60/rev7:default
+
+See the [build environment setup](https://docs.qmk.fm/#/getting_started_build_tools) and the [make instructions](https://docs.qmk.fm/#/getting_started_make_guide) for more information. Brand new to QMK? Start with our [Complete Newbs Guide](https://docs.qmk.fm/#/newbs).