Added installation of pyserial (Arduino-CI/arduino_ci#235) and moved to using OS matrix

Author: skallaher

.github/workflows/windows.yaml renamed to .github/workflows/actions.yaml

@@ -1,4 +1,4 @@
-name: Windows
+name: Run Unit Tests
 
 on: 
   push:
@@ -15,13 +15,23 @@ on:
 
 jobs:
   "unittest_reveng_paj7620":
-     runs-on: windows-latest
+     strategy:
+       matrix:
+         os: [ubuntu-latest, macos-latest, windows-latest]
+     runs-on: ${{ matrix.os }}
      steps:
        - uses: actions/checkout@v2
        - uses: ruby/setup-ruby@v1
          with:
            ruby-version: 2.6
-       - name: Run tests
+       - uses: actions/setup-python@v2
+         with:
+           python-version: '3.x'
+       - name: Install Python Serial
+         run: |
+           python -m pip install --upgrade pip
+           pip install pyserial
+       - name: Run unit tests
          run: |
            g++ -v
            bundle install