How about including Lepton theme?

[black7375]

Hello, I'am author of Lepton custom theme.
I accidentally found your work and looks fun.

What do you think of containing my theme in your browser?
It is the most popular custom theme used by quite a few people, and is also used in various forks such as Warterfox(G4, G5) and Floorp browser, RunningCheese.

[trickypr]

I am going to start looking into this today, but it will take some time. I may need to make some pull requests to your upstream repo to get things working the way I want them to

[trickypr]

This didn't make it in before the feature freeze, so it will not be included in the next stable release. You can follow progress on the tracking issue: #117