message: add node 15 to test suite
diff: @@ -10,7 +10,7 @@ jobs:
  strategy:
  matrix:
  os: [ubuntu-latest]
  - node-version: [10.x, 11.x, 12.x, 13.x, 14.x]
  + node-version: [10.x, 11.x, 12.x, 13.x, 14.x, 15.x]
  include:
  - os: macos-latest
  node: 12.x
  