Add missing nexus-staging-maven-plugin declaration

Author: scordio

pom.xml

@@ -181,6 +181,10 @@
           <outputDirectory>target/site/jacoco</outputDirectory>
         </configuration>
       </plugin>
+      <plugin>
+        <groupId>org.sonatype.plugins</groupId>
+        <artifactId>nexus-staging-maven-plugin</artifactId>
+      </plugin>
     </plugins>
   </build>
 </project>