Add Gruvbox-Dark and Gruvbox-Light themes

[MarshDeer]

No description provided.

[jeffvli]

Looks pretty good! A couple suggestions from me:

1. Convert the color to a rgba value and add opacity for the colors.table.selectedRow color value since solid colors can make it harder to read what's currently selected.
   
   

2. I think the colors.button.default.colorHover is broken (from my code side) so readability is difficult when hovering buttons on Gruvbox Light. I'm currently doing a full application rewrite so I probably won't be fixing it for the time being. I'd suggest choosing a different color and background hover color for the buttons so it's readable.
   

[MarshDeer]

Did the requested fixes and followed the workflow's recommendations re: adding , at the end of some lines.
Themes should hopefully be properly functional now!

[jeffvli]

Thanks!