Executing notebooks with anywidget assist from command line

[psychemedia]

To run a notebook with anywidget wasm support from the command line, we need more than juat access to the pythin interpreter.

One solution would be to run the server and open the notebook into a headless browser, run all cells, save the notebook, close the browser.

For multiple notebooks, keep browser open until all notebooks have executed.

[psychemedia]

Test framework that tests UI features in several Jupyter realted projects runs test by loading notebooks in jupyterlab etc. So reuse that machinery?

[psychemedia]

There is an experimental terminal for JupyterLite; it might be interesting if this could support calls to pglite? Could we do that by borrowing from anywidget?