adjustRotation(delta, anchor) {
    if (anchor) {
      anchor = fromUserCoordinate(anchor, this.getProjection());
    }
    this.adjustRotationInternal(delta, anchor);
  }
Adds a value to the view rotation, optionally using an anchor. Any rotation
constraint will apply.
@param {number} delta Relative value to add to the zoom rotation, in radians.
@param {import("./coordinate.js").Coordinate} [anchor] The rotation center.
@api