Space-triggered '\<symbol>' autocompletion messes up cursor position

[khoek]

If you somehow end up in a situation with \nat (not yet autocompleted) in the middle of a line, such as while editing the tutorial snippets, like;

foo \nat bar baz

and then move your cursor to the end of \nat and press space, your cursor ends up where it would have had you the \nat -> ℕ autocompletion had not occurred, which can be really annoying.

I tried to fix the problem, but I don't really know anything about Monaco. I think we might need to somehow obtain a reference to the monaco editor instance within checkInputCompletion(), and call executeEdits() on the editor instead of applyEdits() on the model.