Update Documentation: Docu out of sync

[hanneslueke]

Is your feature request related to a problem? Please describe.
While using the latest version i was surprised to see that publishAsync returns something i do not know and don't if i should care.

same is true for subscribeAsync but less "severe". instead of the type "granted[]" the type "ISubscriptionGrant[]" is used in the actual code

i

Describe the solution you'd like
Either change the code or update the documentation with a little bit of context regarding the returned object.

[robertsLando]

Could you submit a PR to fix the docs?