Add a short-circuiting version of TransformerFSupport for Either

[mrobakowski]

A short-circuiting version of TransformerFSupport[Either[E, +*]] can be very useful and convenient if your code doesn't particularly care what exactly happened and just needs to know if the conversion failed or not.

I put it in a separate object, so this is a compatible change and requires the user to opt-in via an import.