A webhook for releases has been added and can be set in the space settings. Whenever a release gets merged into the content repository it will trigger a post request with following payload:

{
  "text": "The release summer has been merged.",
  "release_id": 313,
  "space_id": 44953
}

With the release_id you can get a list of stories that have been in that release by making a call to the management api with the parameter from_release: https://www.storyblok.com/docs/api/management#core-resources/stories/retrieve-multiple-stories