chore: use pnpm package manager.

.github/workflows/node.js.yml

@@ -14,10 +14,18 @@ jobs:
     
     steps:
     - uses: actions/checkout@v2
+
+    - name: Install pnpm
+      uses: pnpm/action-setup@v2.0.1
+      with:
+        version: 6.15.1
+
     - name: Use Node.js 14.x
       uses: actions/setup-node@v2
       with:
         node-version: 14.x
+        cache: 'pnpm'
+        
     - run: pnpm install
     - run: pnpm build