Allow real time collaboration

**Is your feature request related to a problem? Please describe.**
I tried to install the module [jupyterlab-link-share](https://github.com/jupyterlab-contrib/jupyterlab-link-share) to support sharing the current notebook and runtime environment, but the share link did not work.

**Describe the solution you'd like**
As mentioned in the document of JupyterLab (https://jupyterlab.readthedocs.io/en/stable/user/rtc.html), the JupyterLab supports collaboration with other users by sharing access to the current notebook plus the runtime environment.

**Describe alternatives you've considered**
The plain JupyterLab supports collaboration from version 3.1, also google Colab supports share functionality which provides a similar way to collaborate.

**Additional context**