document underlying interactive elements

Summary: Document the native elements underlying interactive components, including a link to MDN.

Details: When an interactive component is backed by a native element (e.g <Button> is backed by <button>), documentation must include a reference to the native element (e.g.) to know what additional props will be passed through to that element. In many cases, e.g. <DatePicker> or <MultiSelection>, the underlying components are not obvious and having a direct link to documentation for the backing element can be enormously helpful.