Ci: Test on Sphinx 8 / Dev. (sphinx-contrib#259)

* CI: Testing for latest Sphinx (8.0)

* CI: Fix helper class version checking.

.github/workflows/python-package.yml

@@ -54,6 +54,28 @@ jobs:
         tox -e "${{matrix.python-version}}-sphinx${{matrix.sphinx-version}}-pygments${{matrix.pygments-version}}"
 
 
+  test-sphinx-latest:
+    name: Run tests for Python ${{ matrix.python-version }}, Sphinx ${{ matrix.sphinx-version }},  Pygments ${{ matrix.pygments-version }}
+    timeout-minutes: 5
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        python-version: ["3.10", "3.11", "3.12"]
+        sphinx-version: ["dev"]
+        pygments-version: ["latest"]
+    steps:
+    - uses: actions/checkout@v4
+    - name: Set up Python ${{ matrix.python-version }}
+      uses: actions/setup-python@v5
+      with:
+        python-version: ${{ matrix.python-version }}
+        architecture: x64
+    - name: Run with Tox
+      run: |
+        pip install tox==4.8.0
+        tox -e "${{matrix.python-version}}-sphinx${{matrix.sphinx-version}}-pygments${{matrix.pygments-version}}"
+
+
   test-sphinx-latest:
     name: Run tests for Python ${{ matrix.python-version }}, Sphinx ${{ matrix.sphinx-version }},  Pygments ${{ matrix.pygments-version }}
     timeout-minutes: 5