Allow Imports In Custom CSS Overrides

Problem

Right now, if users put something like so: @import url("https://cdn.jsdelivr.net/gh/scarcekoi/fluxer@main/themes/mocha/mocha-blue.css"); into the Custom CSS Overrides box, it will not load the CSS file. There is a an attempt it looks like, but it seems to get blocked: image

Proposed solution

Make it so CSS files can be imported into the CSS overrides and have live reloading so every x amount of time it will pull the CSS file again.

Notes (optional)

Something like every 15/30 minutes might be good. An option for reload time should probably be provided if an @import is detected so that the user can choose how often they want the file to get checked. Maybe have a manual option to check it whenever the user chooses (Have an option to turn of automatic reload and just have a button the reloads the style).