dev-docs: document E-Mail to STACKIT on every release (#3108)

dev-docs/workflows/release.md

@@ -92,6 +92,13 @@ Releases should be performed using [the automated release pipeline](https://gith
 5. If the release is a minor version release, bump the pre-release version in the `version.txt` file.
 6. Update the `fromVersion` in `e2e-test-release.yml` and `e2e-test-weekly.yaml` to the newly released version. To check the current values, run: `grep "fromVersion: \[.*\]" -R .github`.
 7. Reset `UpgradeRequiresIAMMigration`  in [`iamupgrade.go`](https://github.com/edgelesssys/constellation/blob/a88a731576184e3c5ee8527741c4a0cdaa4e9b24/cli/internal/cloudcmd/iamupgrade.go#L23).
+8. Write an email to STACKIT to inform them of the new relase. For this, you require the name and UUID of the release image. You can find the email address in our internal [wiki](https://github.com/edgelesssys/wiki/blob/master/documentation/constellation/stackit.md):
+    ```shell-session
+    export OS_CLOUD=stackit
+    openstack image list | grep constellation
+    # the output should look similar to this, where the first column is the UUID and the second column is the name
+    # | 25edf48d-161f-452b-b420-963c3a80abd8 | constellation-stable-v2.16.4-qemu-vtpm | active |
+    ```
 
 ## Troubleshooting: Pipeline cleanup