Add gitlab CI with eslint check

.gitlab-ci.yml

+stages:
+  - lint
+
+eslint:
+  stage: lint
+  #image: node:current-alpine3.12
+  image: node:12-alpine3.12
+  tags: [ docker ]
+  script:
+    - npm install
+    #- npm ci ### should use this for automated testing instead of "npm install", but we need a package-lock.json for it.
+    - npm install eslint-formatter-gitlab
+    - npx eslint --format gitlab .
+  # errors make eslint return 1, for now though we want the pipeline not to ail when we eslint errors.
+  # trying to add " ; exit 0" or " ; echo 0" let the build fail anyways for some reason.
+  allow_failure: true
+  artifacts:
+    reports:
+      codequality: gl-codequality.json