Right now we only update remote CSS files if:

• The file URL changes.
• The user clicks synchronize in App Settings.

It could be interesting to improve this, but we need to be careful with increasing the app's network usage.

An option would be to re-download them every certain time, but in most cases the CSS won't be modified once it's done so we might be re-downloading it a lot for nothing.

Another option would be to use a head request and detect file size (or etags if supported), but we don't want to perform too many head requests either.