Upgrade GitHub actions/checkout: v3 => v4

Author: piecioshka

.github/workflows/testing.yml

@@ -18,12 +18,15 @@ jobs:
         node-version: [13.x, 14.x, 16.x]
 
     steps:
-      - uses: actions/checkout@v3
+      - name: Checkout
+        uses: actions/checkout@v4
+
       - name: Use Node.js ${{ matrix.node-version }}
         uses: actions/setup-node@v3
         with:
           node-version: ${{ matrix.node-version }}
           cache: "npm"
+
       - run: npm ci
       - run: npm run build --if-present
       - run: npm run lint --if-present