I'm not happy with the current theme system. We can change only colors, but I would like to change a bit everything, to get something looking for instance like The Lounge:

https://thelounge.chat/

Things I would like to change:
- typography
- borders + shadow and radius
- margins and paddings

It would be quite easy if we could upload a piece of CSS based on a few class selectors. Like:

.app__content {
  box-shadow: 0 0 25px rgba(0, 0, 0, 0.75);
  z-index: 10;
  border-radius: 5px;
}