add testing of multiple opperating systems to mdanalysis-compatibility.yaml

Author: harryswift01

.github/workflows/mdanalysis-compatibility.yaml

@@ -8,11 +8,12 @@ on:
 jobs:
   mdanalysis-compatibility:
     name: MDAnalysis Compatibility Tests
-    runs-on: ubuntu-24.04
+    runs-on: ${{ matrix.os }}
     timeout-minutes: 15
 
     strategy:
       matrix:
+        os: [ubuntu-24.04, windows-2025, macos-15]
         python-version: ["3.11", "3.12", "3.13", "3.14"]
         mdanalysis-version: ["2.10.0"]