Add NumPy arrays to top level prerequisites

[K-Meech]

For #368

This PR adds a note about numpy requirements (+ a link to a lesson that covers numpy) to the top level prerequisites block. It is already mentioned briefly in the detailed list linked at the end of this block, but this makes it clearer at a glance.

I also added bullet points to the a/b/c options, as it was getting harder to read with the extra text.

[github-actions]

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⏱️ Updated at 2026-09-28 19:41:35 +0000

[marcodallavecchia]

Thanks @K-Meech! Looks good to me!

[uschille]

Thanks @K-Meech! Looks good to me as well.