Transfert search parameters from Page URL to Jupyterlite URL

[brichet]

I wonder if we could transfert some search parameters from the URL of the page to the iframeSrc options.

Problem

It is currently not possible to retrieve the search parameters of the page in the Jupyterlite application.

Proposed Solution

Add a new option to the jupyterlite directive with a list of parameters to transfert to the iframeSrc (if the parameters exist).

Additional context

This could be a solution for jupyterlite/litegitpuller#6, because litegitpuller currently use the search param of the jupyterlite URL.