Support extends for typedef

[dobesv]

It would be nice if @extends could be used with @typedef, for example:

/**
 * @typedef {Object} A
 * @prop {string} a
 */
/**
 * @typedef {Object} B
 * @extends A
 * @prop {string} b
 */
/**
 * @typedef {Object} C
 * @extends {Object.<string,object>}
 * @prop {string} c
 */

Would give something like:

// interface syntax
interface A { a : string }
interface B extends A { b: string }
interface C extends Record<string, object> { c: string }

// or type = syntax
type A = { a: string };
type B = A & { b: string };
type C = Record<string, object> & { c: string };