Excalidraw Support

[oripka]

I did some trials to integrate excalidraw and it worked when converting the files to png automatically using a browser as an exporter.

I think it would be nice to be able to draw directly on a slide using excalidraw (or make a new slide during a presentation and draw there) in a sort of editor mode. Then have it persist and be rendered as transparent png that is dark mode aware during the presentation.