Add option to reverse update UI changes

Discord isn't always the greatest with UI changes. This latest update is certainly no exception, though this is the first change I've found to be physically painful on the eyes. Quite a lot of people have already taken to the boards to request a change, but Discord is generally a bit slow with taking feedback into account, and having to struggle to read the text for the next few days to a few weeks before they do anything about it is a very unpleasant prospect. 

My proposal is to add an option in settings to reverse new update UI changes, so that users don't have to struggle with undesired changes before the kinks are all ironed out from feedback on the boards.