WEB: Add pandas cookbook 3 to home page
#61271 was hard reverted, as it contained a 1.4 Mb image which we didn't want in our git history.

Same PR here, but with the image now using 9Kb.

@WillAyd, if you check in detail, you and Matt look a bit like cartoons, hahaha. This is because I'm just using 24 colors in the image, as this makes the file size much smaller than using 256. I don't think anyone will notice, and even when paying attention to me it looks kind of cool, more than anything bad. But I'm surely happy to improve the quality of the image and have an image some Kb bigger if you prefer. Just let me know.
/preview Website preview of this PR available at: https://pandas.pydata.org/preview/pandas-dev/pandas/61279/