fix: "Add registry name in all Docker images"

templates/extract.yml

 # this job extracts the bash script from the given template(s)
 extract-script:
-  image: alpine
+  image: registry.hub.docker.com/library/alpine
   stage: .pre
   script:
     - echo "#!/bin/bash" > script.sh

templates/validation.yml

@@ -46,7 +46,7 @@
   }
 
 gitlab-ci-lint:
-  image: dwdraju/alpine-curl-jq:latest
+  image: registry.hub.docker.com/dwdraju/alpine-curl-jq:latest
   stage: build
   before_script:
     - *lint-scripts