refactor(docker): include dockerRegistry, dockerRepository in results

lib/datasource/docker/index.js

@@ -349,6 +349,10 @@ async function getPkgReleases({ lookupName, registryUrls }) {
     return null;
   }
   const releases = tags.map(version => ({ version }));
-  const ret = { releases };
+  const ret = {
+    dockerRegistry: registry,
+    dockerRepository: repository,
+    releases,
+  };
   return ret;
 }