_createCanvasOfMask(width, height) {
      const maskCanvasEl = fabric.util.createCanvasElement();

      maskCanvasEl.width = width;
      maskCanvasEl.height = height;

      return maskCanvasEl;
    }
Create canvas of mask image
@param {number} width - Width of main canvas
@param {number} height - Height of main canvas
@returns {HTMLElement} Canvas element
@private