This fixes behavior for URLs with single quotes within them.
The behavior for a url like `https://severalglamorousthing.426729.repl.co/google's%20logo.png` would be no background at all; the CSS rule would change to `background-image: url((unknown));`.
This fixes the problem and adds `\` to every `'` in the image url.
The behavior of the repo with this fix would be a conversion of the url provided above to `https://severalglamorousthing.426729.repl.co/google\'s%20logo.png`, which can be put into `\`url('${url}')\`` without breaking the CSS rule.
