ci: add macos to test matrix (#675)

* ci: add macos to test matrix

* re-build

Author: dnalborczyk

.github/workflows/pull_request.yml

@@ -14,7 +14,7 @@ jobs:
     strategy:
       matrix:
         node-version: [12.x, 14.x, 16.x]
-        os: [ubuntu-latest, windows-latest]
+        os: [macos-latest, ubuntu-latest, windows-latest]
     runs-on: ${{ matrix.os }}
     steps:
       - uses: actions/checkout@v2