Function cloneChess

cloneChess(state: ChessState): ChessState
A deep copy, safe to mutate (via applyMove) without touching the original - what legalMoves uses to try a move and check it does not leave the mover in check.
Parameters
- state: ChessState
Returns ChessState
Example
```
import { startingChess, cloneChess } from '@datamoc/mw_games/board';

const state = startingChess();
const trial = cloneChess(state);
console.log(trial !== state, trial.turn); // true 'white'
```
- Defined in src/board/chess.ts:216