use node 16 for browser build tests

Author: lobsterkatie

.github/workflows/build.yml

@@ -410,6 +410,8 @@ jobs:
         uses: actions/checkout@v2
       - name: Set up Node
         uses: actions/setup-node@v1
+        with:
+          node-version: '16'
       - name: Check dependency cache
         uses: actions/cache@v2
         with: