feature request: add support for or filters

[luke-rogers]

In version 9.18, firebase added support for or queries.

From this PR we can see it has been made available via a new query method with the signature query<T>(query: Query<T>, compositeFilter: QueryCompositeFilterConstraint, ...queryConstraints: QueryNonFilterConstraint[]).

Introduction of the new QueryCompositeFilterConstraint type means its incompatible with the current signatures of syncCollection, syncCollectionGroup, and valueChanges and as such or queries cannot be used.

I'd be interested to hear some opinions on the proposed method signatures as there is quite a bit of overloading already going on.

Happy to have a go at adding support if we can agree on the approach.