Add CI step to validate type publication

Author: PeterJCLaw

.github/workflows/python-test.yml

@@ -38,3 +38,20 @@ jobs:
     steps:
       - uses: actions/checkout@v3
       - uses: psf/black@stable
+
+  check-types-published:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+      - uses: actions/setup-python@v5
+        with:
+          python-version: '3.12'
+      - run: |
+          pip install build
+          python -m build --sdist --wheel
+
+          temp=$(mktemp -d)
+          python -m venv $temp/venv
+          $temp/venv/pip install mypy ./dist/*whl
+          echo 'import pythonosc' > $temp/demo.py
+          $temp/venv/mypy $temp/demo.py