Feature: version command

[Opisek]

Given how CodeMirror is used in many different applications, including closed-source ones, I believe adding a :version command would simplify hunting down bugs in the wild. Currently, there is no way to tell the version of CodeMirror-Wim running on some given application.

I can look into implementing that, though it must be discussed what the approach for getting the current version makes the most sense. I would like to avoid hard-coding the value.

[nightwing]

we could use something like #181, but sadly codemirror 6 does not have an equivalent of https://codemirror.net/5/doc/manual.html#version, so we can display only version of codemirror-vim itself

[Opisek]

That looks great. Perhaps it's worth going upstream to implement CodeMirror.version, too? It shouldn't be a difficuilt addition.

[nightwing]

It, indeed, may be useful. I'll update the version command in vim if/when CodeMirror.version is available.

[Opisek]

It seems it might be unlikely to get support upstream:
codemirror/dev#1398

Your addition is already great, though, and will certainly come in helpful in the future.