Add Zen mode to Caucus

[Rishabh-malhotraa]

Add a full sceen zen mode just like on algo expert

        position: 'fixed',
        top: 0,
        right: 0,
        bottom: 0,
        left: 0,
        zIndex: 999

It would also be good if you can have a toolbar for the editor which shows the current language

[GaganpreetKaurKalsi]

Can you please assign this issue to me. I would like to work on it. Thanks!

[GaganpreetKaurKalsi]

It would be great if you can merge this pull request first. After all this was my first major pull request and first one in your repository. Thanks!