Type safe local icon support

[CRBroughton]

Hi there!

I've been using the Icon component both personally and at work; I found that when working with local icon collections, the intellisense I get back from the Icon component is lacking compared to the experience I have with Iconify collections.

If possible I'd like to make a modification that enables type generation for local collections (I already have a good working PR, but it might require some feedback).