DOC: capitalize NumPy as proper noun

[erictleung]

In a similar vein to #37808

• closes #xxxx
• tests added / passed
• passes black pandas
• passes git diff upstream/master -u -- "*.py" | flake8 --diff
• whatsnew entry

[jreback]

is it possible to modify the docs checkers to make sure this in enforced?

[erictleung]

We could add a spelling checker when building Sphinx https://sphinxcontrib-spelling.readthedocs.io/en/latest/index.html. I don't see this extension used in the current conf.py file (https://github.com/pandas-dev/pandas/blob/master/doc/source/conf.py#L52-L69). But of course, this would add to the number of dependencies, which may or may not be wanted.

If there's another place you're referring to, @jreback, I'd be interested to learn.

[jreback]

i think this needs to be a pre-commit hook or maybe we discussed as a code_check. cc @MarcoGorelli

can do later for that i guess.

[MarcoGorelli]

I think a pygrep hook to check that we don't use Numpy (with only the N capitalised) would be OK - @erictleung if you check the other local pygrep hooks in .pre-commit-config.yaml they can provide a guide, feel free to reach out to me for help (here or on the gitter channel) if you want to do this and need help

[jreback]

thanks @erictleung