Remove images loaded from outside the current site

[johnstonphilip]

I am not sure it's a good idea to be directly loading images from a non-local place, like (github or amazons3). Eventually, there will have to be a solution for loading background image files from the current WP's domain, instead of from "the cloud".

For example: https://github.com/WordPress/theme-experiments/blob/master/parisienne/block-template-parts/contact.html#L4

That will need to be adjusted (at some point) to pull from the local domain, though I am not sure how that should be best accomplished. I think this is an important piece to solve if static HTML files are to be the solution for full-site-editing.