Update GitHub Themes

[AntonPieper]

The current "github_dark" and "github_light" themes do not align with the actual GitHub Theme. Maybe it is time to update them (particularly the dark theme) to align with the VSCode GitHub Themes Extension default themes (GitHub Dark Default and GitHub Light Default). If the newer versions are too different, they could also be called "github_dark_default" and "github_light_default" respectively to match the VSCode extension's naming scheme.

[siduck]

prs are welcome

[AntonPieper]

I have tried for a few hours now, the challenging part for me is figuring out what each base30 / base16 value actually represents. To me it seems like many values don't change anything because I am not using the full set of features of NvChad / don't know where to look. It would be nice if there was some example source code file where every color is used or additional information in the docs. Nonetheless I am very great ful for your work and I will keep trying to implement this revision of the GitHub theme

[siduck]

check the readme of this repo

[siduck]

@AntonPieper check base16 guidelines for knowing which var colors which syntax