GitHub Actions: Add Python 3.14 to test matrix

Python v3.14 -- October 7th
* https://www.python.org/download/pre-releases
* https://www.python.org/downloads/release/python-3140rc2

Author: cclauss

.github/workflows/ci.yml

@@ -9,15 +9,16 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        python: ['3.8', '3.9', '3.10', '3.11', '3.12']
+        python: ['3.8', '3.9', '3.10', '3.11', '3.12', '3.13', '3.14']
 
     steps:
       - name: Checkout
-        uses: actions/checkout@v4
+        uses: actions/checkout@v5
       - name: Setup python
-        uses: actions/setup-python@v5
+        uses: actions/setup-python@v6
         with:
           python-version: ${{ matrix.python }}
+          allow-prereleases: true
           cache: pip
           cache-dependency-path: test-requirements.txt
       - name: Run tests
@@ -34,7 +35,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        python: ['3.8', '3.9', '3.10', '3.11', '3.12', '3.13']
+        python: ['3.8', '3.9', '3.10', '3.11', '3.12', '3.13', '3.14']
         check_formatting: ['0']
         extra_name: ['']
         include:
@@ -43,9 +44,9 @@ jobs:
             extra_name: ', check formatting'
     steps:
       - name: Checkout
-        uses: actions/checkout@v4
+        uses: actions/checkout@v5
       - name: Setup python
-        uses: actions/setup-python@v5
+        uses: actions/setup-python@v6
         with:
           python-version: ${{ matrix.python }}
           allow-prereleases: true
@@ -65,14 +66,15 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        python: ['3.8', '3.9', '3.10', '3.11', '3.12']
+        python: ['3.8', '3.9', '3.10', '3.11', '3.12', '3.13', '3.14']
     steps:
       - name: Checkout
-        uses: actions/checkout@v4
+        uses: actions/checkout@v5
       - name: Setup python
-        uses: actions/setup-python@v5
+        uses: actions/setup-python@v6
         with:
           python-version: ${{ matrix.python }}
+          allow-prereleases: true
           cache: pip
           cache-dependency-path: test-requirements.txt
       - name: Run tests