Update Spatial_selection.ipynb notebook

[navidcy]

At the moment this notebook does not run. We need to update it and then add it to the list of automated tests in
https://github.com/COSIMA/cosima-recipes/blob/main/test/test_notebooks.py

If we can make it work with MOM6 output it'd be even better!

[navidcy]

Also good idea is to deal with #267 while updating the notebook

[lidefi87]

I have some code that creates a mask based on a polygon that we can then use to extract data. This would be useful if the study of interest has a boundary that is more complex than a rectangle/square. Do you think this could be added here or it would be better in a new notebook?

[navidcy]

If it's 1-2 cells then definitely add to this notebook. Is it much longer than that?

Also as discussed in #246 we should put this notebook under "Tutorials".

@lidefi87 are you joining tomorrow's hackathon? wanna undertake this task?

[lidefi87]

I think it'll be more than 2 code chunks. Maybe I can make a new example under Tutorials in that case.

I was thinking of joining for about an hour when I go for lunch, which is often later than usual lunch time.