Add new sublime themes

[apiraino]

• Have you checked to ensure there aren't other open Pull Requests for the same update/change?
• Are you doing the PR on the next branch?
• Have you created/updated the relevant documentation page(s)?

This PR adds two more themes for syntax highlighting (Green and RailsBase16 Green Screen Dark).

I've already rebuild and commited the all.themedump (not sure it was a good idea to commit this file).

I've also clarified a bit the relevant documentation.

Thanks for reviewing! And thanks for Zola 8^)

[Keats]

Thanks!