chore: use node.js v16 (openapi-ts#579)

Author: dnalborczyk

.github/workflows/pull_request.yml

@@ -21,7 +21,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        node-version: [12.x, 14.x, 15.x]
+        node-version: [12.x, 14.x, 16.x]
     steps:
       - uses: actions/checkout@v2
       - uses: actions/setup-node@v1