[Keyboard] move niu_mini to /kbdfans (#16112)

keyboards/kbdfans/niu_mini/keymaps/nosarthur/README.md

@@ -0,0 +1,35 @@
+# Kbdfans Niu Mini
+
+Here `keymap.c` is generated by [qmk configurator](https://config.qmk.fm) and
+it corresponds to the colemak-dh layout.
+
+To customize, upload the json file to qmk configurator
+
+- `keymap_colemak_dh.json`: colemak-dh layout
+- `keymap_qwerty.json`: qwerty layout
+
+Make the modification via the web interface, "compile" and download "keymap only".
+Then place the generated `keymap.c` in this folder.
+
+To flush the firmware, connect your keyboard and run
+
+```
+make niu_mini:nosarthur:dtu
+```
+in the `qmk_firmware` source folder.
+There will be some prompts saying no device is found. Click the reset button in
+the back of your keyboard and it should work.
+
+# notes from qmk configurator
+
+This layout was generated by the QMK API. You can find the JSON data used to
+generate this keymap in the file layers.json.
+
+To make use of this file you will need follow the following steps:
+
+* Download or Clone QMK Firmware: <https://github.com/qmk/qmk_firmware/>
+* Extract QMK Firmware to a location on your hard drive
+* Copy this folder into %s
+* You are now ready to compile or use your keymap with the source
+
+More information can be found in the QMK docs: <https://docs.qmk.fm>