Add GitHub dark theme (#127)

Reviewed-on: https://gitea.com/gitea/awesome-gitea/pulls/127
Reviewed-by: delvh <dev.lh@web.de>
Reviewed-by: Denys Konovalov <denyskon@noreply.gitea.com>
Reviewed-by: yardenshoham <yardenshoham@noreply.gitea.com>
Co-authored-by: Rainnny <rainnny@noreply.gitea.com>
Co-committed-by: Rainnny <rainnny@noreply.gitea.com>

README.md

@@ -193,6 +193,7 @@ A curated list of awesome projects related to Gitea and its soft-fork instances.
 - [Dark Blue](https://gitea.artixlinux.org/artix/gitea-dark-blue) - The dark blue Gitea theme used on [https://gitea.artixlinux.org](https://gitea.artixlinux.org)
 - [Dark Red](https://github.com/iamdoubz/Gitea-Dark-Red-Theme) - Dark red theme by iamdoubz
 - [Earl Grey](https://github.com/acoolstraw/earl-grey) - An elegant dark theme for Gitea with blue as highlight color used on [https://git.pinnoto.org/bo](https://git.pinnoto.org/bo)
+- [GitHub](https://github.com/Rainnny7/gitea-github-theme) - A theme to make Gitea look and feel like GitHub.
 - [Matrix](https://github.com/TylerByte666/gitea-matrix-template) - Neon-green with a matrix-inspired background
 - [Pitch Black](https://github.com/iamdoubz/Gitea-Pitch-Black) - Pitch black 1.14+ theme used on [https://git.dou.bet/iamdoubz/Gitea-Pitch-Black](https://git.dou.bet/iamdoubz/Gitea-Pitch-Black)
 - [Tangerine Dream](https://github.com/jager012/tangerine-dream) - Tangerine dark theme for Gitea