Add hooks API to @benzene/ws

[hoangvvo]

We needed to add hooks API like onStart and onComplete to @benzene/ws. We use to have it (#10) but they were removed in a later release due to certain memory leak concerns.

This issue is another visit to this matter. We need to know:

• which hooks are needed
• implementation/api, which variables can be accessed, mutated during those lifecycles.

For inspirations, we can look at https://github.com/apollographql/subscriptions-transport-ws and https://github.com/enisdenjo/graphql-ws.