update example page workflow

.github/workflows/example_page.yml

@@ -7,12 +7,22 @@ on:
 
 jobs:
   examplePage:
-    runs-on: ubuntu-latest
+    runs-on: macos-latest
 
     steps:
       - name: Checkout
         uses: actions/checkout@v2
 
+      - name: Read .nvmrc
+        run: echo ::set-output name=NVMRC::$(cat .nvmrc)
+        id: nvm
+
+      - name: Set Node.js Version
+        uses: actions/setup-node@v1
+        with:
+          node-version: '${{ steps.nvm.outputs.NVMRC }}'
+          registry-url: 'https://registry.npmjs.org'
+
       - name: Build Example Site
         run: |
           npm ci