code: function add(point, rhs) {
      if (typeof rhs === 'number') {
          return {
              x: point.x + rhs,
              y: point.y + rhs,
          };
      } else {
          return {
              x: point.x + rhs.x,
              y: point.y + rhs.y,
          };
      }
  }
docs: add point to point or number
  @param {Point2D} point
  @param {(Point2D | number)} rhs