Here’s an updated version https://glitch.com/edit/#!/fan-haddock
I changed the image spec to be a separate one from the original image spec. That way, it is possible to have both resizable and fixed-size images.
I’m struggling now with a menu item which allows to toggle between normal and resizable images. I tried to create a menu item with the blockTypeItem helper from prosemirror-menu, but that doesn’t work. May i ask for advice on how to implement such a toggle?