Enable / check the Notifications feature for Notebook 7

[jtpio]

JupyterLab 4 adds support for displaying notifications.

We should check whether they work in Notebook 7. Or could be leveraged by third-party extensions.

[jtpio]

Ah looks like the upstream plugin has a hard dependency on IStatusBar at the moment: https://github.com/jtpio/jupyterlab/blob/eeaa6505f658f7eaaad18ea2d7f15c3c5da0b23a/packages/apputils-extension/src/notificationplugin.tsx#L373