Added checkstyle.xml

config/checkstyle/checkstyle.xml

@@ -96,7 +96,7 @@ Checks based on Google Checks, modified for EngineHub.
                      value="Member name ''{0}'' must match pattern ''{1}''."/>
         </module>
         <module name="ParameterName">
-            <property name="format" value="^([a-z][a-z0-9][_a-zA-Z0-9]*|[a-z])$"/>
+            <property name="format" value="^([a-z][_a-zA-Z0-9]*|[a-z])$"/>
             <message key="name.invalidPattern"
                      value="Parameter name ''{0}'' must match pattern ''{1}''."/>
         </module>