Update @type docs to include inline quoted string enums

[coagmano]

As this comment says, the parser has supported these since 2014, but it isn't in the documentation that you can use them

Example:

/**
 * @param {('rect'|'circle'|'ellipse')} shapeType - The allowed type of the shape
 */
Shape.prototype.getType = function (shapeType) {
  return this.type;
};

[coagmano]

Happy to write a PR at home later if nobody else wants to do this