[FEATURE] allow changing the key which looks for the error message

[itsyoboieltr]

Hey, I would like to use this library with Elysia, but Elysia uses the "error" property for custom error messages, instead of "errorMessage". It would be nice if I could tell the library to look for the message in the "error" property instead.

[jtlapp]

What about having this library use errorMessage when present, otherwise using error if present? That way both would be supported without additional configuration?

[itsyoboieltr]

What about having this library use errorMessage when present, otherwise using error if present? That way both would be supported without additional configuration?

That is a completely valid approach! Sounds like something that would work out of the (type)box for most users :D @jtlapp

[jtlapp]

Sorry, I wasn't able to get to it today. Feel free to provide a PR. Just be sure to include tests.