no more appveyor

Author: tcurdt

.github/workflows/ci.yml

@@ -7,9 +7,11 @@ on:
 jobs:
   test:
     strategy:
+      max-parallel: 2
       matrix:
-        java: [ 8, 17 ]
-    runs-on: ubuntu-latest
+        os: [ ubuntu-latest, windows-latest ]
+        java: [ 8, 20 ]
+    runs-on: ${{ matrix.os }}
     steps:
 
       - name: Checkout