What would you like to be added:
To notify WAIT_APPROVAL is failed, I want to get WAIT_APPROVAL_TIMEOUT webhook event, like #5340.

Why is this needed:
I use PipeCD to deploy plenty of microservices, some changes, like changing proto file, may invoke tens of deployments. In that case, I often forget to click approve with WAIT_APPROVAL phase, and also cannot know which deployment reaches WAIT_APPROVAL timeout.