[Keyboard] Add Mechlovin9 rev.3 (#20119)

Co-authored-by: jack <0x6a73@protonmail.com>

keyboards/mechlovin/mechlovin9/rev1/info.json

@@ -4,6 +4,9 @@
         "pid": "0x6509",
         "device_version": "0.0.1"
     },
+    "features": {
+        "backlight": true
+    },
     "backlight": {
         "pin": "B8",
         "breathing": true

keyboards/mechlovin/mechlovin9/rev2/info.json

@@ -4,6 +4,9 @@
         "pid": "0x6509",
         "device_version": "0.0.2"
     },
+    "features": {
+        "backlight": true
+    },
     "backlight": {
         "pin": "D4",
         "breathing": true

keyboards/mechlovin/mechlovin9/rev3/info.json

@@ -0,0 +1,22 @@
+{
+    "keyboard_name": "Mechlovin9 Rev3",
+    "processor": "STM32F103",
+    "bootloader": "stm32duino",
+    "usb": {
+        "pid": "0x6509",
+        "device_version": "0.0.3"
+    },
+    "features": {
+        "backlight": false
+    },
+    "bootmagic": {
+        "matrix": [0, 13]
+    },
+    "matrix_pins": {
+        "rows": ["B12", "B13", "B14", "B15", "A1"],
+        "cols": ["B11", "B10", "B2", "B1", "B0", "A6", "A5", "A4", "A3", "C13", "B7", "B6", "B5", "B4", "B3"]
+    },
+    "indicators": {
+        "caps_lock": "B9"
+    }
+}

keyboards/mechlovin/mechlovin9/rev3/readme.md

@@ -0,0 +1,23 @@
+# mechlovin9
+
+![mechlovin9](https://i.imgur.com/T5Lm6OYlh.png)
+
+A 65% PCB, compatible with Kyuu.
+
+* Keyboard Maintainer: [Team Mechlovin](https://github.com/mechlovin)
+* Hardware Supported: Kyuu Keyboard.
+* Hardware Availability: [Reddit GB](https://www.reddit.com/r/mechmarket/comments/i61par/gb_mechlovin_9_a_kyuu_65_keyboard_compatible_pcb/)
+
+Make example for this keyboard (after setting up your build environment):
+
+    make mechlovin/mechlovin9/rev3:default
+
+Flashing example for this keyboard:
+
+    make mechlovin/mechlovin9/rev3:default:flash
+
+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).
+
+## Bootloader
+
+**Reset Key:** To put the mechlovin9 PCB into bootloader, hold ESC and plug cable.

keyboards/mechlovin/mechlovin9/rules.mk

@@ -7,7 +7,6 @@ EXTRAKEY_ENABLE = yes       # Audio control and System control
 CONSOLE_ENABLE = no         # Console for debug
 COMMAND_ENABLE = no         # Commands for debug and configuration
 NKRO_ENABLE = no            # Enable N-Key Rollover
-BACKLIGHT_ENABLE = yes      # Enable keyboard backlight functionality
 RGBLIGHT_ENABLE = no        # Enable keyboard RGB underglow
 AUDIO_ENABLE = no           # Audio output