document description supplement for #6403 (#6630)

docs/en/setup/service-agent/java-agent/Application-toolkit-log4j-1.x.md

@@ -30,6 +30,8 @@ The gRPC report could forward the collected logs to SkyWalking OAP server, or [S
 ```properties
 log4j.rootLogger=INFO,CustomAppender
 log4j.appender.CustomAppender=org.apache.skywalking.apm.toolkit.log.log4j.v1.x.log.GRPCLogClientAppender
+log4j.appender.CustomAppender.layout=org.apache.log4j.PatternLayout
+log4j.appender.CustomAppender.layout.ConversionPattern=[%t] %-5p %c %x - %m%n
 ```
 
 *  Add config of the plugin or use default

docs/en/setup/service-agent/java-agent/Application-toolkit-log4j-2.x.md

@@ -111,7 +111,9 @@ The gRPC report could forward the collected logs to SkyWalking OAP server, or [S
 * Add `GRPCLogClientAppender` in log4j2.xml
 
 ```xml
-    <GRPCLogClientAppender name="grpc-log"/>
+    <GRPCLogClientAppender name="grpc-log">
+        <PatternLayout pattern="%d{HH:mm:ss.SSS} [%t] %-5level %logger{36} - %msg%n"/>
+    </GRPCLogClientAppender>
 ```
 
 *  Add config of the plugin or use default

docs/en/setup/service-agent/java-agent/Application-toolkit-logback-1.x.md

@@ -118,7 +118,13 @@ The gRPC reporter could forward the collected logs to SkyWalking OAP server, or
 * Add `GRPCLogClientAppender` in logback.xml
 
 ```xml
-    <appender name="grpc-log" class="org.apache.skywalking.apm.toolkit.log.logback.v1.x.log.GRPCLogClientAppender"/>
+    <appender name="grpc-log" class="org.apache.skywalking.apm.toolkit.log.logback.v1.x.log.GRPCLogClientAppender">
+        <encoder class="ch.qos.logback.core.encoder.LayoutWrappingEncoder">
+            <layout class="org.apache.skywalking.apm.toolkit.log.logback.v1.x.mdc.TraceIdMDCPatternLogbackLayout">
+                <Pattern>%d{yyyy-MM-dd HH:mm:ss.SSS} [%X{tid}] [%thread] %-5level %logger{36} -%msg%n</Pattern>
+            </layout>
+        </encoder>
+    </appender>
 ```
 
 *  Add config of the plugin or use default