Gist-based share link

[Nhowka]

With this we can get a shareable link that is friendly in comparison with what we have now. Needs a github token with the gist scope, but it has a link that sends the user to the right place to get one.

May conflict with #48.

[alfonsogarciacaro]

This is really nice @Nhowka, thank you! I assume the "old" way to share code is still valid, right? Would it be also possible to share the code from the REPL to the gist?

Anyways, let's merge this and I'll give it a try to see the possibilities. Thanks again! 🥇

[Nhowka]

Yes, the old way still works. When you add a github token it will add a Share to gist button that will create a gist based link instead of the old one.

[alfonsogarciacaro]

Sorry @Nhowka, I was checking other issues and forgot to update the REPL 😅 I did it now together we other improvements so the gist sharing feature is finally online. It's very cool, thanks a lot for your contribution!