add staging plugin

Author: DQinYuan

pom.xml

@@ -207,6 +207,17 @@
                     <target>1.8</target>
                 </configuration>
             </plugin>
+            <plugin>
+                <groupId>org.sonatype.plugins</groupId>
+                <artifactId>nexus-staging-maven-plugin</artifactId>
+                <version>1.6.7</version>
+                <extensions>true</extensions>
+                <configuration>
+                    <serverId>ossrh</serverId>
+                    <nexusUrl>https://ossrh-staging-api.central.sonatype.com/</nexusUrl>
+                    <autoReleaseAfterClose>true</autoReleaseAfterClose>
+                </configuration>
+            </plugin>
             <plugin>
                 <groupId>org.antlr</groupId>
                 <artifactId>antlr4-maven-plugin</artifactId>