[Keyboard] add kbdpadmk3 (#18795)

Co-authored-by: Ryan <fauxpark@gmail.com>
Co-authored-by: Joel Challis <git@zvecr.com>
Co-authored-by: Drashna Jaelre <drashna@live.com>

keyboards/kbdfans/kbdpad/mk3/readme.md

@@ -0,0 +1,23 @@
+# KBDPAD MK3
+
+An RGB hotswap 21key numpad.
+
+* Keyboard Maintainer: [moyi4681](https://github.com/moyi4681)
+* Hardware Supported: KBDFANS
+* Hardware Availability: [kbdfans](https://kbdfans.myshopify.com/)
+
+
+## Bootloader
+
+Enter the bootloader in 3 ways:
+
+* **Bootmagic reset**: Hold down the key at (0,0) in the matrix
+* **Physical reset button**: Briefly press the button on the back of the PCB
+* **Keycode in layout**: Press the key mapped to `RESET` if it is available
+
+
+Make example for this keyboard (after setting up your build environment):
+
+    make kbdfans/kbdpad/mk3: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).