Merge branch '13-validate-xml-file-in-ci-cd' into 'master'

Resolve "validate xml file in CI/CD"

Closes #13

See merge request !16

.gitlab-ci.yml

+stages:
+  - test
+
+before_script:
+  - rm -f /home/gitlab-runner/.docker/config.json
+
+XML_Lint:
+  stage: test
+  image:
+    name: its-registry.unl.edu/unl-its/docker-ci/xml-lint:latest
+  tags:
+  - iam-pub, dockerd, shell 
+  script:
+    - docker run -v ${PWD}:/work its-registry.unl.edu/unl-its/docker-ci/xml-lint:latest xml-lint /work/ --no-schema