NIU Mini Settings update and Refactor (#6651)

NIU Mini Settings update and Refactor (#6651)

* update codebase to four-space indent

* update codebase to use #pragma once

* refactor config.h

* change info.json to debug linting

* refactor readme

- file header
- update docs links

* minimize and lint rules.mk

* change features

- enable mousekeys and nkro

* use GPIO commands for Status LED

Co-Authored-By: fauxpark <fauxpark@gmail.com>
* use IS_LED_ON macro

Co-Authored-By: fauxpark <fauxpark@gmail.com>
* update compile/flash examples in readme

* :flash doesn't use QMK Toolbox