Problem: Adding themes requires editing code

[weex]

Themes fairly compact as far as file stucture goes and the changes that need to be made to add to the codebase, but adding a theme still requires a PR therefore affecting the ability for an admin to upgrade easily. Inspired by #338

[MakaryGo]

Wouldn't it be possible to do it similar to the current option to include custom CSS?
That's actually how Discourse did solve theming...