20210515_test_node_16.md

Add Node 16 to test suite, drop Node 10

Node 16 soon becomes LTS and Node 10 falls out of support. To make sure your tests are up to date, edit .github/workflows/test-and-release.yml as follows:

- node-version: [10.x, 12.x, 14.x]
+ node-version: [12.x, 14.x, 16.x]