Add MonsGeek M3

[LLuuDev]

Description

Adds the V3 definition for the MonsGeek M3 (TKL ANSI, RGB Matrix).

• VID/PID 0xFFFE / 0x0009, matrix 6x17, matching keyboards/monsgeek/m3/keyboard.json in QMK master
• Uses qmk_rgb_matrix_keycodes (firmware uses RM_* keycodes)
• Custom lighting menu lists only the RGB Matrix animations enabled in the firmware, in QMK's effect order
• Formatted with the repository's Prettier config; npm run build passes locally against current master

QMK Pull Request

qmk/qmk_firmware#20542 (merged)

VIA Keymap Pull Request

The VIA keymap was merged into QMK with the keyboard itself (qmk/qmk_firmware#20542, before 0.26.0), so there is no separate userspace PR. It was carried over into VIA userspace main and is already there:

• https://github.com/the-via/qmk_userspace_via/tree/main/keyboards/monsgeek/m3/keymaps/via
• the-via/qmk_userspace_via@604e329

Checklist

• The VIA support for this keyboard is MERGED in QMK master already (MANDATORY)
• VIA keymap is MERGED in VIA userspace master already (MANDATORY)
• The VIA definition follows the guide here: https://caniusevia.com/docs/layouts
• I have a V3 JSON version for this keyboard definition.(MANDATORY)
• I have used explicit QMK lighting keycode modules instead of the legacy qmk_lighting module.
• I have formatted the JSON file to have consistent formatting with the rest of the repository.
• I have tested this keyboard definition using VIA's "Design" tab.
• I have tested this keyboard definition with firmware on a device.
• I have assigned alpha keys and modifier keys with the correct colors.
• The Vendor ID is not 0xFEED