feat: comment statuscolumn & foldtext

[folke]

Describe what this PR does / why we need it

This PR fixes both issues/features as described in #80:

• use statuscolumn on Neovim >= 0.9 for rendering comment signs, so that they render correctly when wrapping
• use foldtext on Neovim >= 0.10 for better rendering of folded comments/threads/...

Does this pull request fix one issue?

Fixes #80

Describe how you did it

I implemented both a statuscolumn and foldtext.
See the two different commits.

Describe how to verify it

In Neovim 0.10, check the features described

Special notes for reviews

In the screenshot you can see comment markers from a wrapped comment.
And what a folded thread looks like (lighter background)

Edit: I seem to have included the code from my other PR as well :)

[pwntester]

Thats awesome, thanks! I had some basic statuscolumn recommendations in the README but I like the idea of building it in. Will review ASAP.

[pwntester]

Thanks again @folke!

[folke]

Thanks for merging!

One thing I just thought about is that signs.place is also used when not part of signs.place_signs in the file-entry module.

The new statusline impl, won't show those signs right now, but I can add them as well.

I'm still pretty new to octo, so where can I see that file-entry being used?