Merge pull request #174 from msgpack/ci-node16

[CI] add nodejs v16

Author: gfx

.github/workflows/ci.yml

@@ -12,7 +12,7 @@ jobs:
 
     strategy:
       matrix:
-        node-version: ['12', '14']
+        node-version: ['12', '14', '16']
 
     steps:
     - uses: actions/checkout@v2