ci(workflow): add 'npm' cache for actions/setup-node in .github/workflows

.github/workflows/test.yml

@@ -3,25 +3,25 @@ on:
   push:
     branches:
       - main
-  pull_request:
-
+  pull_request: null
 jobs:
   test:
     runs-on: ubuntu-latest
     steps:
-    - name: Checkout
-      uses: actions/checkout@v2
+      - name: Checkout
+        uses: actions/checkout@v2
+
+      - name: Set Node.JS
+        uses: actions/setup-node@v2
+        with:
+          node-version: 12.x
+          cache: npm
 
-    - name: Set Node.JS
-      uses: actions/setup-node@v2
-      with:
-        node-version: 12.x
+      - name: Install dependencies
+        run: npm install
 
-    - name: Install dependencies
-      run: npm install
+      - name: Build
+        run: npm run build
 
-    - name: Build
-      run: npm run build
-    
-    - name: Run tests
-      run: npm run test
+      - name: Run tests
+        run: npm run test