setup testing for python 3.13 (#53)

Author: zingale

.github/workflows/flake8.yml

@@ -21,7 +21,7 @@ jobs:
       - name: Install Python 3.11
         uses: actions/setup-python@v5
         with:
-          python-version: '3.10'
+          python-version: '3.11'
           cache: "pip"
 
       - name: Install pylint

.github/workflows/pytest-all.yml

@@ -17,7 +17,7 @@ jobs:
 
     strategy:
       matrix:
-        python-version: ["3.9", "3.10", "3.11", "3.12"]
+        python-version: ["3.10", "3.11", "3.12", "3.13"]
 
     steps:
       - uses: actions/checkout@v4