Add operation types from change events

[ksshlee]

I've added operation types from MongoDB change events

reference : https://www.mongodb.com/docs/manual/reference/change-events/

[ksshlee]

@rozza hi! could you please check this pull request??

[rozza]

@ksshlee thanks for the PR. I'm no longer working on the connector, but I've added KAFKA-425 to track this for the connector team.

It should be triaged in the near future.

[ksshlee]

@rozza thanks!