Add SINGA Kohaku

[itsme-zeix]

Description

Add VIA support for SINGA Kohaku

QMK Pull Request

qmk/qmk_firmware#24309

VIA Keymap Pull Request

https://github.com/the-via/qmk_userspace_via/pull/19/files

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 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

[Cipulot]

@itsme-zeix keymap in the VIA rep was approved, if this PR is ok to be reviewed for merge flag it and I'll get to it asap. Asking since I don't want to review and possibly merge something that may not be 100% final and up to date, flagging it will tell me that it's ready.
Cheers

[itsme-zeix]

@Cipulot Done! Thank you so much for the quick review! Really appreciate the work you've done taking over some of the VIA maintenance.