Add support for Coban Pad 3A

[RyanDam]

Description

Add new keyboard: Coban Pad 3A.
Coban Pad 3A is small macro keyboard with 2 hotswapable button and 1 EC11 rotary encoder

Note: I original created PR #1653 but it is closed due to my PR to QMK is not merged. Now it is merged.

QMK Pull Request

qmk/qmk_firmware#19634

Checklist

• The VIA support for this keyboard is in QMK master already (MANDATORY)
• The VIA definition follows the guide here: https://caniusevia.com/docs/layouts
• 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

[Xelus22]

Is there any legacy pcbs with V2? As this has just been merged. (we're trying to not add anything to V2 moving forward unless in extreme circumstances). If not please remove the V2 (src folder) defintion.

[RyanDam]

Is there any legacy pcbs with V2? As this has just been merged. (we're trying to not add anything to V2 moving forward unless in extreme circumstances). If not please remove the V2 (src folder) defintion.

@Xelus22 I'm not aware that V2 is deprecated, now V2 is deleted.