Added subscribeBy(DisposableContainer, [...]) extensions.

[mickverm]

RxJava 3.1.0 was released, which contains the following change:

• API addition: subscribe([...], DisposableContainer) for better Disposable management and reference cleanup.

I've added the following extension methods with named arguments;

Observable<T>.subscribeBy(DisposableContainer, onError, onComplete, onNext)
Flowable<T>.subscribeBy(DisposableContainer, onError, onComplete, onNext)
Single<T>.subscribeBy(DisposableContainer, onError, onSuccess)
Maybe<T>.subscribeBy(DisposableContainer, onError, onComplete, onSuccess)
Completable.subscribeBy(DisposableContainer, onError, onComplete)

:warning: RxJava 3.1.0 requires minimum Android API 21 (Android 5.0)

[akarnokd]

Hi. This repo is quite old and would need to be updated to GitHub Actions. I have no experience with gradle-kotlin so can't really help with it. RxJava's workflows may be a useful template.