Support transformation schema for YAML

[RVRhub]

The PR introduces yaml transformer.
An example of usage

Faker faker = new Faker();
System.out.println(
    new YamlTransformer<Name>().generate(
        faker.collection(faker::name).len(1).build(),
        Schema.of(field("name", Name::fullName), field("username", Name::username))));

Result:

name: Mabelle Prohaska
username: clara.lemke

[snuyanzin]

hi @RVRhub nice to see you here
thanks for your contribution
in general lgtm, i left a nit comment