DOC: Include unrendered style notebook in git, execute in build

[TomAugspurger]

Did this for statsmodels the other week, works pretty well. Something like

jupyter nbconvert --ExecutePreprocessor.timeout=600 --to html --execute style.ipynb

https://nbconvert.readthedocs.org/en/latest/execute_api.html

[jreback]

yep - even better this actually catches errors
say you have a missing import

the only issue is if you have a deliberate exception (u need to put it in a markdown block instead)

[TomAugspurger]

This will have to wait on nbconvert 4.2, which let's you specify the kernel when executing. I believe it's being released soon.

[jorisvandenbossche]

Closed by #13225