[client] Improve docs wrt. client.listen and returned observable and how to unsubscribe (#1239)
[client] Improve docs wrt. client.listen and returned observable and how to unsubscribe (#1239)

Clarified how to unsubscribe from a listen query, and fixed/added a few links to official RxJS-docs
sanity-io/sanity,sanity-io/sanity,sanity-io/sanity,sanity-io/sanity