Pre-install additional packages with emscripten-forge

Using the xeus-python kernel, you can pre-install packages from either conda-forge or emscripten-forge by specifying them in the environment.yml file in the JupyterLite build directory.

By pre-installing packages, they are readily usable in the kernel and can be imported without the need of installing them in the notebook with micropip or piplite.

When pre-installing packages that provide JupyterLab extensions (e.g. ipywidgets or ipyleaflet), those JupyterLab extensions are automatically included in the JupyterLite build output without the need for extra configuration.

As an example, a deployment can easily be made using the JupyterLite deployment demo with xeus-python.

This demo follows the same steps as the quickstart guide but uses Xeus Python as the kernel.