Explicitly call 'npm run lint' in CI test pipeline

This starts the linting process (npm run lint)
explicitly in the CI test pipeline because the
implicit call in the npm run test command does not
break the pipeline, even if there are linting
errors.

.github/workflows/ci-tests.yml

@@ -14,4 +14,5 @@ jobs:
 
       - run: npm ci
       - run: npm run init:app
+      - run: npm run lint
       - run: npm run test