NSClean notebook example for fixed slit mode

[melanieclarke]

This PR completes the NSClean demonstration series for NIRSpec modes. This example shows how to use the currently available NSClean package with full-frame and subarray fixed slit modes.

The notebook has been reviewed by the NIRSpec team, including the fixed slit mode lead. We'd like to get this example out now, since subarray usage in particular is not well documented.

All of the NSClean demo notebooks will need to be revised when the algorithm is implemented in the pipeline (currently in progress), but we expect they will still be useful to provide, since the new step will be optional and will likely need manual tuning for most users.

[melanieclarke]

Thanks, @sosey.

I agree, it seems a bit odd to have the instructions in the notebook itself, since you have to leave and come back to use them. I figured you can at least see the instructions in the rendered notebook online, so maybe you can read the intro, take those steps first, then run the notebook.

I think the JDAT notebooks generally provide a requirements.txt file alongside their notebooks, which might be useful if users knew to look for them. In this particular case, since NSClean is not available via pip or conda, it needs specific instruction anyway, and I'm not sure where that could be provided other than in the notebook itself.

[melanieclarke]

@sosey - can we merge this one now?

[sosey]

@melanieclarke I'm fine with it. After I submitted my review it should have been up to you and @PatrickOgle the other reviewer, do you not have a green on the rebase and merge? It only requires one approval I believe

[melanieclarke]

I see, thanks. I'll go ahead and merge.