Lock repository to lts/fermium (node v14)

.github/workflows/checks.yml

@@ -14,6 +14,11 @@ jobs:
       - name: Checkout code
         uses: actions/checkout@v2
 
+      - name: Setup Node.js environment (v14)
+        uses: actions/setup-node@v2
+        with:
+          node-version: 'lts/fermium'        
+
       - name: Install npm dependencies
         if: always()
         run: |