Feature request: custom theme tt-dark

[Tim Tiefenbach]

I have made some small changes to the "photon-dark" theme in a separate branch of forked repo here (to match the color scheme to my website). I'm not sure how to go from here, should I PR this to merge it with the upstream master? Are small changes to a theme OK or would you require a unique new theme for an official PR?

Thanks in advance.