Cleanup and compress image.

.drone.yml

@@ -13,6 +13,8 @@ steps:
       registry: https://cs-registry.ddnss.de
       repo: cs-registry.ddnss.de/${DRONE_REPO_OWNER}/prometheus
       dry_run: false
-      purge: false
+      purge: true
+      squash: true
+      compress: true
       tags:
       - ${DRONE_TAG}