Add current working directory as first config path

[blink1073]

Fixes #228

[jasongrout]

Thanks!

[ccordoba12]

I think this will introduce CVE-2022-21699 in projects that rely on Jupyter-core, so perhaps it should be reverted?

[kevin-bates]

I just installed the pre-release and am finding that lab/workspaces is being created in my home directory, abandoning the same already in ~/.jupyter. With the switch to platformdirs, there's an opt-in element for the 5.x release. Is this worthy of the same? Otherwise, folks will "lose" their current settings and those settings are now visible (by default) if their root-dir happens to be their home directory.