Add node 16.x to CI

Author: Trygve Lie

.github/workflows/test.yml

@@ -8,7 +8,7 @@ jobs:
     strategy:
       matrix:
         os: [ubuntu-latest, macOS-latest, windows-latest]
-        node-version: [12.x, 14.x]
+        node-version: [12.x, 14.x, 16.x]
     steps:
       - uses: actions/checkout@v2
       - name: Use Node.js ${{ matrix.node-version }}