Move checkstyle linter to its own job (#87)

.github/workflows/ci.yaml

@@ -25,6 +25,18 @@ jobs:
         with:
           args: /github/workspace
 
+  checkstyle:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+      - uses: actions/setup-java@v3
+        with:
+          distribution: temurin
+          java-version: 11
+          cache: maven
+      - run: mvn -B -ntp dependency:go-offline
+      - run: mvn -B -ntp checkstyle:check
+
   codeql:
     runs-on: ubuntu-latest
     permissions:
@@ -52,7 +64,7 @@ jobs:
           server-username: SERVER_USERNAME
           server-password: SERVER_PASSWORD
       - run: mvn -B -ntp dependency:go-offline
-      - run: mvn -B -ntp verify
+      - run: mvn -B -ntp verify -Dcheckstyle.skip
         if: ${{ github.ref != 'refs/heads/main' }}
       - run: mvn -B -ntp deploy
         if: ${{ github.ref == 'refs/heads/main' }}