[Feature request] Configure a response body to use when receiving webhooks

[lorisleiva]

We've received this feature request by email.

Currently Octohook replies the same response for every single webhook received: a 200 with an empty body.

Some webhook providers might have different expectations and it would be nice to allow users to configure their response body using a JSON editor. It might also be helpful to allow them to configure the successful response status.

Note that I don't think this is something we could or should allow to configure within the workflow since the initial webhook response should be as fast as possible to avoid unnecessary retries.