Add DICE emulator for machines without a CPU.

[mittonk]

Builds and runs on a RPi 4 (Bookworm 64).
Builds and runs on a RPi Zero 2w (official RetroPie image, Buster 32).
(Unusably slow on a RPi B+.)

No targeted database/scraper yet. 1-2 games match using the "arcade" scraper config.
No theme yet Basic theme in es-theme-carbon-2021.

[mittonk]

Added arcade option based on @cmitu 's feedback.

[mittonk]

Use arcade scraper config for dice directory.

Note that the arcade directory doesn't yet support ".dmy" files --- should I add those like ".fba" files, or avoid mucking with an important file list and say in the docs that .dmy files need to be in dice/ ?

[joolswills]

Thank you for this. Not had time to test yet but looks good!.