doc: Add example for ParameterName into xdoc

src/xdocs/config_naming.xml

@@ -1034,6 +1034,15 @@ public boolean equals(Object o) {
     <property name="ignoreOverridden" value="true"/>
 </module>
           </source>
+        <p>
+          An example of how to configure the check for names that begin with
+          a lower case letter, followed by letters and digits is:
+        </p>
+        <source>
+&lt;module name="ParameterName"&gt;
+    &lt;property name="format" value="^[a-z][a-zA-Z0-9]+$"/&gt;
+&lt;/module&gt;
+        </source>
       </subsection>
 
       <subsection name="Example of Usage">