Add Support for Chess Variants

[Phillyclause89]

Add Support for Chess Variants

Description:
Extend the functionality of the ChessMoveHeatmap library to support popular chess variants. This enhancement would make the library more versatile and appealing to a broader audience.

Suggested tasks:

1. Research the rules and unique mechanics of popular chess variants such as:
   • Chess960 (Fischer Random Chess)
   • Crazyhouse
   • King of the Hill
   • Horde Chess
2. Adapt the existing heatmap generation logic to accommodate the unique rules of these variants (e.g., randomized starting positions in Chess960 or piece drops in Crazyhouse).
3. Update the API or user interface to allow users to specify the variant when generating a heatmap.

Acceptance Criteria:

• Heatmaps can be generated for at least one additional chess variant (e.g., Chess960).
• The library documentation is updated to include details about supported variants.
• Existing functionality for standard chess remains unaffected.

[Phillyclause89]

After careful consideration, I've decided to close this issue as Not Planned.

The functionality for supporting chess variants will be deferred to external libraries like python-chess. If their chess.Board and chess.pgn.Game classes support a specific chess variant, users may theoretically use those objects with this library to some degree. However, I will not be providing any guarantees or conducting testing for such use cases.