normalizeTweenValue = (propName, value, $el, i, targetsLength) => {
  let v = getFunctionValue(/** @type {any} */(value), $el, i, targetsLength);
  if (!isNum(v)) return v;
  if (commonDefaultPXProperties.includes(propName) || stringStartsWith(propName, 'translate')) return `${v}px`;
  if (stringStartsWith(propName, 'rotate') || stringStartsWith(propName, 'skew')) return `${v}deg`;
  return `${v}`;
}
@param  {String} propName
@param  {WAAPIKeyframeValue} value
@param  {DOMTarget} $el
@param  {Number} i
@param  {Number} targetsLength
@return {String}