upgrade node version 16->20 in github action

Author: huan

.github/workflows/gh-pages.yml

@@ -21,7 +21,7 @@ jobs:
 
       - uses: actions/setup-node@v2
         with:
-          node-version: 16
+          node-version: 20
           cache: 'npm'
           cache-dependency-path: package.json
       - name: NPM Install
@@ -55,7 +55,7 @@ jobs:
 
     - uses: actions/setup-node@v2
       with:
-        node-version: 16
+        node-version: 20
         cache: 'npm'
         cache-dependency-path: package.json