external spellchecker plugin (port of vis-spellchecker)

What? Neovim port of https://github.com/fischerling/vis-spellcheck . I have started something at https://github.com/mcepl/nvim-spellcheck, but I have not enough time to do anything about it.

Why? I am strong supporter of https://github.com/neovim/neovim/issues/12064 and anything which makes me able to get rid of that blasted internal spellchecker is a plus in my books.

More brownie-points if you can manage to keep the code portable so that improvements could be shared with the original vis-spellchecker plug-in.

Potential existing implementations: See above, https://github.com/mcepl/nvim-spellcheck

Potential pitfalls: Simple port of the vis-spellchecker plug-in should be easy to do, making perfect replacement of the internal spellchecker will be probably more involved.

Also, if you follow all suggestions on https://github.com/neovim/neovim/issues/12064 then some of them are quite obviously from Architecture Astronauts. KISS!