Support for "onCreateRequestBody" hook

Hello! Thank you everyone for this amazing library, its been working wonderfully for me. I have a few features in mind for the library but one simple add might be a couple new hooks that allow us to modify type generation. It took me a while to figure out why the `onCreateRequestParams` hook was not firing on my apis (they take `body` rather than `query`). I'd like to be able to easily hook into the type creation for requests if possible.

Here is where the [onCreateRequestParams](https://github.com/acacode/swagger-typescript-api/blob/35b08b114be05a5163861f3a1570477bd577d672/src/routes.js#L279) hook is defined.

Does this seem like a reasonable solution or should I consider a different route for supporting what I need?