@Nonnull
    static CompositeTerminable createWeak() {
        return new AbstractWeakCompositeTerminable();
    }
Creates a new standalone {@link CompositeTerminable}, which wraps
contained terminables in {@link java.lang.ref.WeakReference}s.

@return a new {@link CompositeTerminable}
helper/src/main/java/me/lucko/helper/terminable/composite/CompositeTerminable.java