[Keyboard] Add NK20 (#17907)

Co-authored-by: Joel Challis <git@zvecr.com>
Co-authored-by: yiancar <yiancar@gmail.com>

keyboards/novelkeys/nk20/readme.md

@@ -0,0 +1,32 @@
+# NK20
+
+This is a standard fixed layout Numpad PCB. It supports VIA and full per-key RGB.
+
+* Keyboard Maintainer: [Yiancar](https://yiancar-designs.com/) and on [GitHub](https://github.com/yiancar)
+* Hardware Supported: A Numpad keyboard with STM32F072CB or APM compatible
+* Hardware Availability: https://novelkeys.com/
+
+## Instructions
+
+### Build
+
+Make example for this keyboard (after setting up your build environment):
+
+    make novelkeys/nk20: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).
+
+### Reset
+
+- Unplug
+- Hold Escape
+- Plug In
+- Unplug
+- Release Escape
+
+### Flash
+
+- Unplug
+- Hold Escape
+- Plug In
+- Flash using QMK Toolbox or dfu-util (`make novelkeys/nk20:<keymap>:dfu-util`)