github project: https://github.com/kofifus/prosemirror-spellchecker
demo: https://plnkr.co/edit/Mo7nNAucTRROs0rM4npu
Basically the plugin setts spellcheck=false on the ProseMirror’s div, then does it’s own parsing using a fork of Typo.js, it then adds the wriggly red lines under typos as decorations, and hooks a suggestion box on right click.
While it seems to be working fine, this is more of a proof of concept than a done deal and it hasn’t been tested heavily (one known bug is that pasting multiple lines does not check their content, also right clicks seem fidgety).
thx!