feat(theme): GitHub Material Theme

**Note**: This is not exactly a continuation of https://github.com/StylishThemes/GitHub-Dark/pull/568. I just mostly used coloring rules from the Twilight Theme which looks the most consistent and replaced the colors with Material colors from [here](https://github.com/material-theme/vsc-material-theme/blob/7850c56ad75ab690524b7ecbe4f853c8b68e42e9/scripts/generator/settings/specific/default.ts). So this is essentially Twilight Theme (in terms of color rules) but with Material colors. Please let me know if you prefer it to be a continuation of https://github.com/StylishThemes/GitHub-Dark/pull/568 instead, I can close this if that is the case.