feat(gitsigns): support GitSignsCurrentLineBlame highlights

[kang8]

Description

I found that the fg color of GitSignsCurrentLineBlame and Comment are the same, which sometimes confuses me:

The Comment fg color is overlay0 now:

nvim/lua/catppuccin/groups/syntax.lua

Line 5 in dae42a0

Comment = { fg = C.overlay0, style = O.styles.comments }, -- just comments

GitSignsCurrentLineBlame is mapped to NonText:

https://github.com/lewis6991/gitsigns.nvim/blob/749267aaa863c30d721c9913699c5d94e0c07dd3/lua/gitsigns/highlight.lua#L174

And, NonText fg color is same with Comment:

nvim/lua/catppuccin/groups/editor.lua

Line 30 in dae42a0

NonText = { fg = C.overlay0 }, -- '@' at the end of the window, characters from 'showbreak' and other characters that do not really exist in the text (e.g., ">" displayed when a double-wide character doesn't fit at the end of the line). See also |hl-EndOfBuffer|.

What problem does this PR solve?

This PR distinguishes the two, making the GitSignsCurrentLineBlame dimmer and making it easier to distinguish between the two.

Actual effect

Latte

• before

• after

Frappe

• before

• after

Macchiato

• before

• after

Mocha

• before

• after