Mancala (27b8690b292cc3b612debb26a40609bb882c0ab4) - refactoring drawing code to the BoardUI class

game.js

...
const {BoardUI} = require("./drawing.js")
...

class MancalaGame
{
  constructor (...)
  {
    ...
    this.boardUI = new BoardUI(cnvsELID,this.cellCount,this)
    this.boardUI.initializeBoardDrawing();
  }
  
  _redraw()
  {
    this.boardUI.drawBoardState(this.board,this);
  }
  
  togglePlayer()
  {
    this.player = this.player.theOtherOne();
    this.boardUI.toggleHighlights(this.player.number);
    return this.player;
  }
  
}