Show how to use John Resig's class.extend pattern

[hegemonic]

As noted in jsdoc/jsdoc#1371, we don't currently provide an example of how to document code that uses John Resig's class.extend pattern. It would be useful to add this to the docs.

[hegemonic]

Actually, we mostly document this on the @lends tag page. At a minimum, though, we should update these examples to include the @classdesc tag.