Add setup step for Python 3.12

Author: bjsowa

.github/workflows/ci.yml

@@ -41,6 +41,11 @@ jobs:
         with:
           version: 3.28.3
 
+      - name: Setup Python
+        uses: actions/setup-python@v6
+        with:
+          python-version: '3.12'
+
       - uses: ros-tooling/setup-ros@v0.7
 
       - uses: ros-tooling/action-ros-ci@v0.4