Types: Add entry for QUnit's Assert type

Ref jquery/api.qunitjs.com#58

This implements "1) We put all types on api.jquery.com, even if they have nothing to do with jQuery" from https://github.com/jquery/grunt-jquery-content/issues/54
If it's a reference _to_ the object, then this should read: "A reference to or instance of the object&hellip;"