drop support for Python 3.9 (#158)

Author: radoering

.github/workflows/main.yaml

@@ -19,7 +19,7 @@ jobs:
     strategy:
       matrix:
         os: [Ubuntu, macOS, Windows]
-        python-version: ["3.9", "3.10", "3.11", "3.12", "3.13", "3.14"]
+        python-version: ["3.10", "3.11", "3.12", "3.13", "3.14"]
         include:
           - os: Ubuntu
             image: ubuntu-latest