DEPR: deprecate Series/DataFrame.compound
xref https://github.com/pandas-dev/pandas/issues/18262

Not sure if we need to point to an alternative in the deprecation warning. I can put the exact "formula" for what we are currently calculating, but I don't know enough from finance to know if that is actually good to point to (eg I don't directly see that formula on the first google hit https://en.wikipedia.org/wiki/Compound_interest)