Convert drawing to static PNG (or SVG)

[kolibril13]

There are already two functions for that : TldrawMakeStaticPNG, TldrawMakeStaticSVG.
However, after converting the PNG (or SVG) is still a widget, and therefore won't be displayed after notebook reopening and also won't be displayed on GitHub.

In order to make this work, the jupyter cell output would need to be converted to the type image/jpeg.
This is an unsolved ipywidget issue, but this minimal example might help figuring thing out:
jupyter-widgets/ipywidgets#3874