This theme is an unffocial port of the GitHub Dark theme (I can't find any other themes right now - it seems that I am the first person to recreate this theme!). Due to the differences between how GitHub and Graviton check and tokenize code for highlighting there will be small differences, but I have tried to keep this theme as accurate as possible
This theme has been tested in Graviton v2.1
As of the time of writing (early December, 2020), there are some issues with where the default release of graviton2 looks for its plugin files on macOS. To fix this, open up the advanced settings JSON file, find the appConfigPath key, and change it's value to /Users/<yourusername>/graviton2. Now create a folder in your home directory called graviton2, as well as a folder inside graviton2 called plugins.
Open a new terminal and move to the plugins directory you just created. Now run
git clone https://github.com/gaetgu/githubdark-graviton.gitIf everything worked correctly, the GitHub Dark theme should be available in settings once graviton is restarted.
If you have any suggestions or improvements, please create an issue or a discussion (they're new, too!).