feature: gitsigns word diff highlight colors

[diego898]

Did you check the docs?

• I have read all the tokyonight.nvim docs

Is your feature request related to a problem? Please describe.

Hello, I'd like to see if its possible to add support for correct coloring of gitsigns add/remove word diff highlight groups. I just checked, and tokyonight also doesnt have this.

Describe the solution you'd like

removed sections are highlighted in "red" (whatever the appropriate color is)
added/changed sections are highlighted in "green" (whatever the appropriate color is)