feat: Support non-GitHub repositories

[OmarIthawi]

This one goes without saying. Some maintainers would need to pull from Gitlab or their own git repo.

Atlas should allow any git repository to be used:

• --repository=openedx/openedx-translations: A single / found, therefore assumes GitHub repo slug and clones https://github.com/openedx/openedx-translations.git

• --repository=https://github.com/test/our-translations.git: https:// is found therefore assumes full URL and checks out https://github.com/test/our-translations.git

• --repository=git@gitlab.com:another/translations.git: @ is found, therefore assumes full URL and checks out git@gitlab.com:another/translations.git