Provide a diff in the task.updated webhook

I want to use the task.updated webhook to detect when a task is moved from or out of the doing bucket.
Especially the latter is not easy in the current system, as the previous state is not provided from what I am seeing - only the current task state.

How about providing the previous task state, a diff or a list of the changed properties for the task?

Would love a PR for this.

The task would need to be fetched before any updates and then added here.