Typecheck typeshed's code with pyright (#9793)

Co-authored-by: Alex Waygood <Alex.Waygood@Gmail.com>
Co-authored-by: Jelle Zijlstra <jelle.zijlstra@gmail.com>

.github/workflows/typecheck_typeshed_code.yml

@@ -40,3 +40,31 @@ jobs:
           cache-dependency-path: requirements-tests.txt
       - run: pip install -r requirements-tests.txt
       - run: python ./tests/typecheck_typeshed.py --platform=${{ matrix.platform }}
+  pyright:
+    name: Run pyright against the scripts and tests directories
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        python-platform: ["Linux", "Windows"]
+      fail-fast: false
+    steps:
+      - uses: actions/checkout@v3
+      - uses: actions/setup-python@v4
+        with:
+          python-version: "3.9"
+          cache: pip
+          cache-dependency-path: requirements-tests.txt
+      - run: pip install -r requirements-tests.txt
+      - name: Get pyright version
+        uses: SebRollen/toml-action@v1.0.2
+        id: pyright_version
+        with:
+          file: "pyproject.toml"
+          field: "tool.typeshed.pyright_version"
+      - name: Run pyright on typeshed
+        uses: jakebailey/pyright-action@v1
+        with:
+          version: ${{ steps.pyright_version.outputs.value }}
+          python-platform: ${{ matrix.python-platform }}
+          python-version: "3.9"
+          project: ./pyrightconfig.scripts_and_tests.json