feat: add blink.cmp hlgroups (proceeds #263)

[WieeRd]

Adds highlight groups for blink.cmp.

Fixed version of #263, which was using completely wrong highlight items.
Added support for ghost texts and label details as well.

[jonsch318]

Thanks yes i would have fixed it today :). I opened it in November, since then Blink has changed drastically, thus my highlight groups are wrong now.
However this is problematic because blink is still in beta and we should expect changes. So either:

1. We/You update this pull-request until it is merged and then always keep it updated with changes from blink
2. Or we wait until blink stabilizes (if ever) and then add it

[jonsch318]

But yes especially the BlinkCmpItemKind => BlinkCmpKind things i just missed. Although i still use it and it looks fine :/ Thanks for correcting it anyway

[WieeRd]

Oh, I should have been a bit more patient, just a few more hours.
I didn't know that highlights were named differently on earlier versions,
apologies on my rude review comment on your original PR.

Although i still use it and it looks fine :/

I assume you couldn't notice the breaking change due to the fallback to nvim-cmp highlights option. This option is planned to be removed in the future, so we do need explicit blink.cmp highlights.

However this is problematic because blink is still in beta and we should expect changes

Seeing how many Neovim related projects stay in 0ver for years, I doubt waiting for the stabilization is a good idea. And having outdated highlights in the config doesn't do much harm other than wasting a few nanoseconds of startup time. I'd say it's better to have this merged now and update it as blink.cmp evolves. Also I don't think there will be much reason to change highlight names yet again (hopefully).

I won't be having much time to spare this year. So if yet another breaking change happens to blink.cmp before this PR gets merged, please create a proceeding PR like I did. @jonsch318

[jonsch318]

I am largely finished with my thesis so i will have more time this year 👍

And yeah i will try to keep looking for breaking changes