Add link to docs when filesystem list is empty

[seibert]

If there are no filesystems configured, the extension should show the user a hyperlink to the juypter-fsspec docs on how to add sources. This is especially important because the first release won't have a UI to add a source. (Coming later!)

[seibert]

This depends on #17

[ericsnekbytes]

This is in progress.

[RRosio]

Note: 9f5e1b2 has been merged to main, so maybe this can be closed as fixed?

[ericsnekbytes]

Yes it can!