jQuery.parseJSON: Function has multiple return types, not just Object.

The return type is currently documented as [`Object`](//api.jquery.com/Types/#Object), with the description "...returns the resulting JavaScript object."

As this function is roughly equivalent to [`JSON.parse`](http://www.ecma-international.org/ecma-262/5.1/#sec-15.12.2), it technically produces an ECMAScript value, which, in addition to `Object` (or, really, [`PlainObject`](//api.jquery.com/Types/#PlainObject)), can also include `String`, `Number`, `Array`, `Boolean`, or `null`. These multiple return types should be explicitly mentioned on the return type.

Shall I attach a PR to make this change and update the description? To further clarify, perhaps another example could be added? (Related, minor issue: There's a rogue line break towards the end of the [current example](//api.jquery.com/jquery.parsejson/#entry-examples)...)