[Keyboard] Add Mixi (#9364)

* [Keyboard] Add Mixi

Co-authored-by: Ryan <fauxpark@gmail.com>

Co-authored-by: Ryan <fauxpark@gmail.com>

keyboards/mixi/rules.mk

@@ -0,0 +1,27 @@
+# MCU name
+MCU = atmega32u4
+
+# Bootloader selection
+#   Teensy       halfkay
+#   Pro Micro    caterina
+#   Atmel DFU    atmel-dfu
+#   LUFA DFU     lufa-dfu
+#   QMK DFU      qmk-dfu
+#   ATmega32A    bootloadHID
+#   ATmega328P   USBasp
+BOOTLOADER = caterina
+
+# Build Options
+#   comment out to disable the options.
+#
+BOOTMAGIC_ENABLE = no       # Virtual DIP switch configuration
+MOUSEKEY_ENABLE = no        # Mouse keys
+EXTRAKEY_ENABLE = yes       # Audio control and System control
+CONSOLE_ENABLE = yes        # Console for debug
+COMMAND_ENABLE = yes        # Commands for debug and configuration
+SLEEP_LED_ENABLE = no       # Breathing sleep LED during USB suspend
+NKRO_ENABLE = no            # USB Nkey Rollover - if this doesn't work, see here: https://github.com/tmk/tmk_keyboard/wiki/FAQ#nkro-doesnt-work
+BACKLIGHT_ENABLE = no       # Enable keyboard backlight functionality
+RGBLIGHT_ENABLE = yes       # Enable keyboard RGB underglow
+ENCODER_ENABLE = yes
+AUDIO_ENABLE = no