fix(editor): make TabLine more readable

[igorlfs]

Hello!

Currently, the TabLine foreground is too dark, barely readable with an even darker background:

After:

[vollowx]

LGTM! BTW I wonder if we should modify TabLineSel highlight to use the same bg as Normal and a text fg, in order to present a more modern look， similar to the default colorscheme.

[igorlfs]

We could make TabLine's background even darker by using crust. Coupled with TabLineSel = { link = "Normal" }, here's how it looks:

Thoughts?

[vollowx]

make TabLine's background even darker by using crust

That make the selected one stand out, looks really nice, and we should also modify TabLineFill to use the same crust bg

[igorlfs]

That make the selected one stand out, looks really nice, and we should also modify TabLineFill to use the same crust bg

Hey! I guess it'd be somewhat nice to have the fill with a different color. That's not very common within neovim, but feels more modern IMO. Perhaps @mehalter could have some input, since he (re)introduced TabLineFill some weeks ago.

[mehalter]

I don't have too much opinion here. If there is a good other color to use then that's probably good if it is more modern. Without it in there at all it was quite distracting so as long as there's a good choice I'm good with it :) plus if I disagree it's easy enough to change locally!