Suggestion: allow loading container list from a remote .txt or .cvs file

[catfluoride]

Hi!

At the moment, this wonderful add-on doesn't support FF Sync for containers list. Nonetheless, an elegant (and, I guess, easier to implement) workaround would be to allow loading containers list from a local or (better yet) a remote url.

One could then host a .txt ot .cvs file on a cloud provider (or even on github), and use a direct https:// URL to said file to load the containers list on all of the user's machines.

Something similar is done, for example, by https://github.com/proginosko/LeechBlockNG (see attached image)

Thanks!