Add Gruvbox Dark Hard variant

[asadmoosvi]

Is it possible to add the Gruvbox Theme with the hard darker background? It's essentially the same Gruvbox Dark theme but with a background color of #1d2021 instead of #282828. I know I can just change the background after installing the theme but I want it to be automated.

[aadilayub]

Similarly, it'd be nice to have a soft variant of this theme

[Mgldvd]

https://github.com/Gogh-Co/Gogh/pulls?q=Gruvbox