Notification email

There was a similar additional to the module that actually inspired this one.
See here: https://git.drupalcode.org/project/config_notify/-/merge_requests/1/diffs

Feel free to work on it, otherwise I can give it a go whenever I have time.

We can probably close this issue now with ✨ Make stuck migrations message configurable Active having it made into the module. You now can override the message per config split or settings.php and provide the env name or URL from there.