Support Neogit highlight groups

[joeveiga]

Hello!
It'd be nice to have hl groups defined for Neogit, if possible. See:

https://github.com/NeogitOrg/neogit/blob/master/doc/neogit.txt

Thank you!

[NovaViper]

Is there any progress on this? It's currently extremely hard to use neogit because of the yellow on green text for the added changes

An example of the problem: