message: Add Node.js 15.x to the GitHub Actions test rotation.
diff: @@ -12,7 +12,7 @@ jobs:
  runs-on: ${{ matrix.os }}
  strategy:
  matrix:
  - node_version: ['10', '12', '14']
  + node_version: ['10.x', '12.x', '14.x', '15.x']
  os: [ubuntu-latest]
  steps:
  