Update main.yml

Author: pivovarit

.github/workflows/main.yml

@@ -15,7 +15,7 @@ jobs:
     strategy:
       matrix:
         os: [ ubuntu-latest, macos-latest ]
-        java: [ 8, 11, 17, 19 ]
+        java: [ 8, 11, 17, 19, 21 ]
     runs-on: ${{ matrix.os }}
     steps:
       - uses: actions/checkout@v3