ci: add plotly to downstream tests

.github/workflows/downstream_tests.yml

@@ -232,3 +232,43 @@ jobs:
         run: |
             cd tubular
             pytest tests --config-file=pyproject.toml
+
+  plotly:
+    strategy:
+      matrix:
+        python-version: ["3.12"]
+        os: [ubuntu-latest]
+
+    runs-on: ${{ matrix.os }}
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-python@v5
+        with:
+          python-version: ${{ matrix.python-version }}
+      - name: Install uv
+        uses: astral-sh/setup-uv@v3
+        with:
+          enable-cache: "true"
+          cache-suffix: ${{ matrix.python-version }}
+          cache-dependency-glob: "**requirements*.txt"
+      - name: clone-plotly
+        run: |
+            git clone https://github.com/plotly/plotly.py --depth=1
+            cd plotly.py
+            git log
+      - name: install-basics
+        run: uv pip install --upgrade tox virtualenv setuptools --system
+      - name: install-deps
+        run: |
+            cd plotly.py
+            uv pip install -r packages/python/plotly/test_requirements/requirements_312_optional.txt --system
+      - name: install-narwhals-dev
+        run: |
+            uv pip uninstall narwhals --system
+            uv pip install -e . --system
+      - name: show-deps
+        run: uv pip freeze
+      - name: Run pytest on plotly express
+        run: |
+            cd plotly.py
+            pytest packages/python/plotly/plotly/tests/test_optional/test_px