Add a "Default working directory" option when sharing a link

[PierreRaybaut]

When sharing a link using the "Windowed interface (JupyterLab)" interface style (see below), it would be nice to have an additional "Default working directory" or "Default current path" option.

This "Default working directory" option would allow selecting the default working directory when opening JupyterLite.
For example, in arepository where the notebooks to be shared are located in a folder named "notebooks" (as in the example below): that's the folder you want to show right away when JupyterLite starts up.

Thanks for considering this feature, and keep up the good work!