CI: also try Python 3.13 (at this time beta 1)

.github/workflows/tox.yml

@@ -14,6 +14,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
+        unsupported: [false]
         os:
          - ubuntu-latest
          # not defaulting to macos-latest: Python <= 3.9 was missing from macos-14 @ arm64
@@ -35,6 +36,14 @@ jobs:
          # https://github.com/actions/runner-images/issues/9741
          - os: macos-latest
            python-version: "3.12"
+           unsupported: false
+         # will run these without showing red CI results should they fail
+         - os: macos-latest
+           python-version: "3.13"
+           unsupported: true
+         - os: ubuntu-latest
+           python-version: "3.13"
+           unsupported: true
     steps:
       - uses: actions/checkout@v4
       - name: Using Python ${{ matrix.python-version }}
@@ -44,10 +53,14 @@ jobs:
           cache: pip
           cache-dependency-path: requirements_test.txt
           check-latest: true
+          allow-prereleases: ${{ matrix.unsupported }}
       - name: Install Dependencies
         run: |
           python -m pip install --upgrade pip
           python -m pip install tox
       - run: tox -e run-module
+        continue-on-error: ${{ matrix.unsupported }}
       - run: tox -e run-entrypoint
+        continue-on-error: ${{ matrix.unsupported }}
       - run: tox -e py
+        continue-on-error: ${{ matrix.unsupported }}