fix node version

Author: iBinh

.github/workflows/gh-pages.yml

@@ -19,7 +19,7 @@ jobs:
       - name: Use Node.js
         uses: actions/setup-node@v1
         with:
-          node-version: '12.x'
+          node-version: '14.x'
       - name: Build website
         run: |
           yarn bootstrap