_setPanWithFriction(axis, potentialPan, customFriction) {
    const {
      currSlide
    } = this.pswp;

    if (!currSlide) {
      return;
    }

    const {
      pan,
      bounds
    } = currSlide;
    const correctedPan = bounds.correctPan(axis, potentialPan); // If we are out of pan bounds

    if (correctedPan !== potentialPan || customFriction) {
      const delta = Math.round(potentialPan - pan[axis]);
      pan[axis] += delta * (customFriction || PAN_END_FRICTION);
    } else {
      pan[axis] = potentialPan;
    }
  }
Set pan position of the current slide.
Apply friction if the position is beyond the pan bounds,
or if custom friction is defined.

@private
@param {'x' | 'y'} axis
@param {number} potentialPan
@param {number} [customFriction] (0.1 - 1)