[FEATURE]: Support other chess Variants

[medegw01]

Checklist

• I checked, but didn't find any duplicates (open OR closed) of this issue in the repo.
• I have read the contribution guidelines
• This issue contains only one feature request. I will open one issue for every feature I want to request.

Describe the feature you want

I think it would be nice to be able to play other chess variants. The following should be supported:

• Crazyhouse
• King of the Hill
• Three-check
• Antichess
• Atomic
• Horde
• Racing Kings
• chess960

Is your feature request related to a problem? Please describe it

I wanted to play Craze house but the engine seems to only now standard chess rules

Additional context

Please see how it was handled in chessops. Also see how top engines handle variation, especially chess960

How will you/everyone benefit from this feature?

This feature will help raccoon to conquer aliens that plays other chess formats