Add new watch event types

[jocelynthode]

Hey, I'm using pykube in a project and I wanted to make use of watches to know when a Job is completed (for example 10/10 successful tasks). I had hoped watches could tell me when a task is completed and indeed it appears everytime a task completes I get a MODIFIED watch event.

Unfortunately This is mixed up with other modified events from the same job meaning I cannot reliably use it. Would it be possible to create a new watch event type for this use case ?