Add a feedback category to discuss UI/UX issues

The support page has a big ol' link labeled “Discord's Interface” that helps people figure out how to use it, but the feedback forum doesn't have a similar link where we can specifically discuss how to make Discord easier and more fun to use? Makes no sense to me 🤔

In fact the support homepage and the feedback homepage seem like they were designed by two completely different teams; or perhaps intended for what one team thinks is their audience and what kinds of feedback they think is important.