Add javadocJar validation job

Signed-off-by: utzcoz <utzcoz@outlook.com>

.github/workflows/gradle_tasks_validation.yml

@@ -49,6 +49,23 @@ jobs:
       - name: Run aggregateDocs
         run: ./gradlew clean aggregateDocs
 
+  run_javadocJar:
+    runs-on: ubuntu-22.04
+
+    steps:
+      - uses: actions/checkout@v3
+
+      - name: Set up JDK
+        uses: actions/setup-java@v3
+        with:
+          distribution: 'zulu'
+          java-version: 11
+
+      - uses: gradle/gradle-build-action@v2
+
+      - name: Run javadocJar
+        run: ./gradlew clean javadocJar
+
   run_instrumentAll:
     runs-on: ubuntu-22.04