Add support for posey_split keyboards

[joliverMI]

Adding posey_split layouts to VIA

Description

Adding support for version 4 and 5 of posey_split.

This keyboard has a hardware repeat function that can be customized by users in VIA.
The LED colors indicate which type of layer is active and if caps is activated. Those colors can be selected by users using VIA as well.

QMK Pull Request

qmk/qmk_firmware#23258

Checklist

• The VIA support for this keyboard is MERGED in QMK 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 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

[joliverMI]

@Cipulot I'm trying to figure out how to get the checks to run on my PR. Not trying to rush you! Just noticed this PR didn't have a checkmark.

[Cipulot]

@joliverMI I'll look at the PR now and suggest changes if needed, otherwise I'll run the checks and merge 👍

[Cipulot]

@joliverMI pull the latest changes that I pushed and then please move the files from the 'src' folder to the 'v3' folder. being this a new board and not a legacy one it is mandatory to use the V3 defines.