safe-money-xmlbf-0.1: README.md

This library exports `FromXml` and `ToXml` instances (from the `xmlbf`
library) for many of the types exported by the `safe-money` library.

Note: The code in this library used to be part of the `safe-money`
library itself, so these instances are intended to be backwards
compatible with older versions of `safe-money`.