added maven javadoc plugin

pom.xml

@@ -113,6 +113,13 @@
                     </execution>
                 </executions>
             </plugin>
+
+            <!-- Javadoc -->
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-javadoc-plugin</artifactId>
+                <version>3.3.2</version>
+            </plugin>
         </plugins>
     </build>