Add Python 3.13 to GitHub Actions CI

Author: mbrukman

.github/workflows/main.yml

@@ -42,7 +42,7 @@ jobs:
       fail-fast: false
       matrix:
         os: [ 'ubuntu-24.04', 'ubuntu-22.04' ]
-        python: [ '3.12', '3.11', '3.10', '3.9','3.8' ]
+        python: [ '3.13', '3.12', '3.11', '3.10', '3.9', '3.8' ]
 
     runs-on: ${{ matrix.os }}
     name: Python ${{ matrix.python }} on ${{ matrix.os }}