Would you be interested in shipping an auto-generated module that can be used as type annotation?

That way people could just do the following:

@webhook.hook()
def on_push(data: webhook.events.Push):
    data['<tab>

and get autocompletion in e.g. PyCharm.

Octokit provides a versioned schema: https://github.com/octokit/webhooks/blob/v3.11.2/index.json