Adding ClassSubject#isAnnotatedWith(Class)

How does Truth feel about adding things to ClassSubject?

There are assertions that I'd like to make using reflection (e.g. `assertThat(someClass).isAnnotatedWith(Singleton.class);`) that aren't currently supported without custom subjects. Is there any strong feeling for or against adding at least this assertion?

I haven't thought very deeply about inheritance, and there are probably arguments to be made in that area. If there isn't any opposition, I'll fork and get to work on it.

Thanks!