setup nodejs 12 on the ci

.github/workflows/build.yml

@@ -8,6 +8,10 @@ jobs:
     steps:
     - name: Checkout
       uses: actions/checkout@v2
+    - name: Setup NodeJS
+      uses: actions/setup-node@v2
+      with:
+        node-version: '12'
     - name: Install NPM dependencies
       run: npm install
     - name: Build