Enable CI for shell-tools

This patch enables the shell tool CI in the main CI run. While it might
looks recursive, it shouldn't be a problem since our CI process works 

.gitlab-ci.yml

 include:
-  local: /gitlab-ci-template.yml
+  - local: /gitlab-ci-template.yml
+  - local: /resources/shell-tools/.gitlab-ci.yml
 
 stages:
+  - shell-tools-lint
+  - shell-tools-test
   - build
   - test
   - tag

resources/shell-tools/.gitlab-ci.yml

-image: docker.io/library/fedora:31
+stages:
+  - shell-tools-lint
+  - shell-tools-test
 
-shellcheck:
+
+shell-tools-shellcheck:
+  image: docker.io/library/fedora:33
+  stage: shell-tools-lint
   before_script:
     - dnf install -y ShellCheck
   script:
-    - shellcheck ./**/*.sh
+    - shellcheck ./resources/shell-tools/**/*.sh
 
-test:
-  image: quay.io/sheogorath/build-ah-engine
+shell-tools-test:
+  image: $CI_REGISTRY_IMAGE:latest
+  stage: shell-tools-test
   script:
-    - test/latest.sh
-    - test/fix-dockerfile-pinning.sh
+    - ./resources/shell-tools/test/latest.sh
+    - ./resources/shell-tools/test/fix-dockerfile-pinning.sh