feat(boards): Polarity works CKP Series

Adds support for the CKP family of boards
BT60V2 ANSIHotswap, ISO Hotswap, ANSI Lowpro and soldered
BT65 ANSI Hotswap, ISO Hotswap and soldered
BT75 ANSI Hotswap and soldered

The BT65 and BT75 are stylised as btXX_v1 in order to maintain compatibility with customers existing zmk-config setups in the same way the BT60 V1 was handled when merged into main.

CKP boards have identical pinmapping between hotswap and soldered so there's only one set of defconfig, dts, keymap, yaml and yml files per size

app/boards/arm/ckp/bt75_v1.zmk.yml

@@ -0,0 +1,14 @@
+file_format: "1"
+id: bt75_v1
+name: BT75_V1
+type: board
+arch: arm
+features:
+  - keys
+  - encoder
+  - underglow
+  - backlight
+outputs:
+  - usb
+  - ble
+url: https://polarityworks.com/btckp