Allow subclasses in typedef comments

[trezm]

At the moment, we ignore the first argument of typedef comments, i.e. for a comment

/**
 * @typedef {Person} Jeff
 */

We ignore the Person super class. We should:

• Be able to follow an inheritance chain to detect if methods/properties exist on a type
• Be able to tell outside of duck-typing if one class is a subtype or equal to another