Inject `nwbfile` code snippet in python console to ensure it also runs on juypyterlab

Currently we load `nwbfile` with the file being looked at. However, it'll be good to insert the command itself in the python console so that the script can then be used elsewhere also, like in the jupyterlab workspace on v2.

Begin at the existing nwbfile loading path and its Python console entry point; verify how the current file context is exposed. Then check the JupyterLab v2 workflow and define done as the generated nwbfile command appearing in the console and remaining usable in that workspace.

Written by the indexing model from the issue text.