UI updates

So... We have all the new UIs. New Friends List. New Create World. Now, it's the Edit World's turn! Firstly, I'd like to have a toggle for the new UIs and the old ones, like the "switch to new UI" thing in Preview/Beta (I love the new ones. It's just that basically nobody else does.) And then also make the UI, colorful!* This will add a nice touch to all the UIs. And also, please add a dark mode. Thank you! *Check the comments for Colorful Containers