Support ability to strip notebooks on version saves

[MSeal]

Using nbstripout, enable publish or version saving to strip outputs before sharing.

https://github.com/kynan/nbstripout

[rgbkrk]

🤔 Would this be "for all time" on a deployment of a notebook server or something else? What are the reasons for wanting this?

For the deployment at Netflix we'd definitely want to keep outputs (?) because our users expect them for sharing, at least for what's effectively latest.

[MSeal]

The intention of the idea was to give the option on automatic saves or publish to be able to publish a clean version of the notebook.

But unlike git, we're not stuck with large outputs polluting history forevermore, so the value in direct integration may be lower here.