Feature Request: Transparent pages

[Erudition]

I would love to use pennywise to create transparent overlays, such as showing the keyboard layout I'm trying to learn. This is possible in e.g. OBS using a browser that allows see-through pages when background-color: transparent is set. I can't find anything that can do this in a normal floating window though, and Pennywise is so close! I know Electron supports this capability.