Add maven-source-plugin to time oracle project

Author: MakarovS

exonum-java-binding/time-oracle/pom.xml

@@ -63,6 +63,11 @@
         <groupId>org.apache.maven.plugins</groupId>
         <artifactId>maven-javadoc-plugin</artifactId>
       </plugin>
+
+      <plugin>
+        <groupId>org.apache.maven.plugins</groupId>
+        <artifactId>maven-source-plugin</artifactId>
+      </plugin>
     </plugins>
   </build>
 </project>