Feature request: better highlighting for fold indicators in FileHistory

[simonmandlik]

Currently in file history fold_open and fold_closed characters use CursorLineNr:

diffview.nvim/lua/diffview/scene/views/file_history/render.lua

Line 88 in 4516612

comp:add_text((entry.folded and c.signs.fold_closed or c.signs.fold_open) .. " ", "CursorLineNr")

I am using signcolumn with background so I want CursorLineNr to have some background but not in diffview file history. I would propose either:

1. definining DiffviewCursorLineNr defaulting to CursorLineNr working the same way as e.g. DiffviewCursorLine
2. using DiffviewNonText instead of CursorLineNr as is the case with file panel

If you think it makes sense, I will gladly prepare a PR