unittests.yml: Add macOS to the testing

[cclauss]

jobs:
  build:
    strategy:
      matrix:
          include:
            - os: macos-latest
              python-version: "3.13"

      - name: Install Python dependencies (macOS, 3.13)
        if: runner.os == 'macOS'
        run: |
          brew install portaudio
          python -m pip install pocketsphinx standard-aifc setuptools
          python -m pip install --no-build-isolation .[dev,audio,whisper-api]