Webhook Response Transform

### Is your proposal related to a problem?

Let's have not only request_transform but also response_transform not only for JSON but also for XML.

Use case: Hasura Action for S3 API:

https://docs.aws.amazon.com/AmazonS3/latest/API/API_CreateMultipartUpload.html
https://docs.aws.amazon.com/AmazonS3/latest/API/API_CompleteMultipartUpload.html
https://docs.aws.amazon.com/AmazonS3/latest/API/API_AbortMultipartUpload.html

### Describe the solution you'd like

Support not only JSON but also XML.
Transform also response.

### Describe alternatives you've considered

Serverless function

### If the feature is approved, would you be willing to submit a PR?

Sure