Some nice features from Livebook.dev

[lucifer1004]

Livebook is an online collaborative notebook for Elixir language, and I think there are a few nice-to-have features for Pluto.jl, including:

• Realtime collaboration: multiple users can edit the notebook simultaneously, just like in Google Doc etc.

• Editable outline:

• Rubbish bin for deleted cells

• Resource usage information

[lucifer1004]

I should have put it in the discussion section initially. My bad.