Also build on Java 21

Author: ThexXTURBOXx

.github/workflows/maven.yml

@@ -14,7 +14,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        java: [ '8', '11', '17' ] # LTS versions
+        java: [ '8', '11', '17', '21' ] # LTS versions
 
     steps:
     - uses: actions/checkout@v3