Issue on TypeScript `FieldRenderProps` typings

https://github.com/final-form/react-final-form/blob/a3ca5f169da5cb5abcf53d60285d8d43b08c427f/typescript/index.d.ts#L25

This typing does not work well with other react libraries.

For example with `rc-select`: http://react-component.github.io/select/#select-props
in the `onChange` prop you don't have access to the event, but only the value selected.

This is valid also for `onFocus` and `onBlur` props