ci(charts): Add publishing mechanism for helm charts

.gitlab-ci.yml

 ---
 include:
   - local: 'images/**/.gitlab-ci.yaml'
+  - local: 'charts/**/.gitlab-ci.yaml'
 stages:
   - release
   - build

charts/mok/.gitlab-ci.yaml

+build:
+  stage: build
+  image: quay.io/helmpack/chart-testing:v3.6.0
+  script:
+    - export TMP_DIR=$(mktemp -d)
+    - helm package charts/* -d "$TMP_DIR"
+    - for i in $(ls $TMP_DIR/*.tgz); do curl --request POST --user "gitlab-ci-token:$CI_JOB_TOKEN" --form "chart=@${i}" "${CI_API_V4_URL}/projects/${CI_PROJECT_ID}/packages/helm/api/${CI_COMMIT_REF_SLUG}/charts"; done
+  rules:
+    - if: '$CI_COMMIT_BRANCH == $CI_DEFAULT_BRANCH && $CI_PIPELINE_SOURCE == "push"'
+      changes:
+        - charts/mok/Chart.yaml