ci: test on node 16

Author: ChristianMurphy

.github/workflows/gh-page.yml

@@ -17,7 +17,7 @@ jobs:
       - name: Use Node
         uses: actions/setup-node@v2
         with:
-          node-version: 15
+          node-version: 16
 
       - name: Use cached node_modules
         uses: actions/cache@v2

.github/workflows/main.yml

@@ -11,7 +11,7 @@ jobs:
     strategy:
       matrix:
         platform: [ubuntu-latest, windows-latest, macos-latest]
-        node-version: [12, 14, 15]
+        node-version: [12, 14, 16]
 
     name: '${{ matrix.platform }}: node.js ${{ matrix.node-version }}'