Add lazy loading attribute

[SUPERCILEX]

Fixes #78

[DirtyF]

From what I understand the loading attribute is meant for images and iframes, not scripts.

What you want here is maybe something like defer or async? https://developer.mozilla.org/en-US/docs/Web/HTML/Element/script

[SUPERCILEX]

Oops! Yeah, I thought I'd read that it worked with scripts, but I just checked and the attribute is ignored. I also tried async and defer, but both of those break rendering for some reason.