Add linter and minor bug fixes (#107)

.github/workflows/workflow.yml

@@ -24,11 +24,27 @@ jobs:
       - name: Run tests
         run: docker run --workdir=/metrics --entrypoint="" lowlighter/metrics:${{ github.head_ref || 'master' }} npm test
 
+  # Run linter to ensure new code respect coding rules
+  lint:
+    name: Apply linter
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v2
+      - name: Setup NodeJS
+        uses: actions/setup-node@v2
+        with:
+          node-version: 15
+      - name: Setup metrics
+        run: npm ci
+      - name: Run linter
+        run: npm run linter
+
   # Run CodeQL on branch
   analyze:
     name: Analyze code
     runs-on: ubuntu-latest
-    needs: [ build ]
+    needs: [ lint ]
     steps:
       - name: Checkout repository
         uses: actions/checkout@v2
@@ -44,7 +60,7 @@ jobs:
   docker-master:
     name: Publish master to GitHub registry
     runs-on: ubuntu-latest
-    needs: [ build ]
+    needs: [ build, lint ]
     if: github.event_name == 'push' && github.ref == 'refs/heads/master'
     steps:
       - name: Checkout repository