refactor preview to use actual html file instead of building its own html

I have so many issues now I feel like I already created this one and I can't find it anymore -_-

Anyways, making html w/ javascript is okay - that's what react does, after all - but at a certain point (now) it starts to become finnicky unless you want to build out your own version of react, which I certainly do not have time for. Also I'm missing syntax highlighting and intellisense for my html.

Theoretically using this method should make rendering the preview faster as would no longer be rendering the entire damn page.