Feature request: support for IgnoreCase & IgnoreCaseAll SpringData methods

Hi.

I added a test in https://github.com/fakemongo/fongo/pull/362 as an example of what I'd wish fongo would provide.

Thoses methodes are described in [Spring Data MongoDB Reference Doc](https://docs.spring.io/spring-data/mongodb/docs/current/reference/html/#repositories.query-methods.query-creation)

How complex would it be to introduce support for those queries ?