Update binder env to install jupyter_rfb from pip

[almarklein]

This:

• Makes that we can use mybinder to test the wheel on Pypi :)
• Should reduce the time it takes to create a fresh mybinder Docker image.

[almarklein]

Also, here's the link to one of our examples, opening it in Jupyter lab:

https://mybinder.org/v2/gh/vispy/jupyter_rfb/binder?urlpath=lab/tree/examples/hello_world.ipynb

Once this is merged, it should be:

https://mybinder.org/v2/gh/vispy/jupyter_rfb/main?urlpath=lab/tree/examples/hello_world.ipynb

[djhoese]

I personally think jupyter lab should be the default. Jupyter notebook will be deprecated eventually as far as I understand:

https://jupyterlab.readthedocs.io/en/stable/getting_started/overview.html

JupyterLab will eventually replace the classic Jupyter Notebook. Throughout this transition, the same notebook document format will be supported by both the classic Notebook and JupyterLab.

[djhoese]

Also you could put a mybinder link to a jupyter lab session right on the README