When getting a stream from a collection.watch, it should be possible to access cursorState to wait for a stream to be ready.

My use case: I'm using WebSockets to let the client know when a specific collection change occurs. If I don't wait for the stream to be ready, it could happen that the client never gets informed about the collection change.

This resulted from a question at stackoverflow: https://stackoverflow.com/questions/56699849/how-do-i-know-when-a-stream-node-js-mongodb-is-ready-for-changes/56708456#56708456