add unicode docs

core/src/main/java/com/taobao/arthas/core/command/klass100/OgnlCommand.java

@@ -30,7 +30,7 @@ import com.taobao.middleware.cli.annotations.Summary;
 @Name("ognl")
 @Summary("Execute ognl expression.")
 @Description(Constants.EXAMPLE
-                + "  ognl '@java.lang.System@out.println(\"hello\")' \n"
+                + "  ognl '@java.lang.System@out.println(\"hello \\u4e2d\\u6587\")' \n"
                 + "  ognl -x 2 '@Singleton@getInstance()' \n"
                 + "  ognl '@Demo@staticFiled' \n"
                 + "  ognl '#value1=@System@getProperty(\"java.home\"), #value2=@System@getProperty(\"java.runtime.name\"), {#value1, #value2}'\n"

site/src/site/sphinx/en/faq.md

@@ -70,6 +70,13 @@ watch demo.MathGame primeFactors '{params,returnObj,throwExp}' 'params.length >0
 watch demo.MathGame <init> '{params,returnObj,throwExp}' -v
 ```
 
+##### Enter Unicode characters
+
+Convert Unicode characters to `\u` representation:
+
+```bash
+ognl '@java.lang.System@out.println("Hello \u4e2d\u6587")'
+````
 
 ##### java.lang.ClassFormatError: null, skywalking arthas compatible use
 

site/src/site/sphinx/faq.md

@@ -69,6 +69,13 @@ watch demo.MathGame primeFactors '{params,returnObj,throwExp}' 'params.length >0
 watch demo.MathGame <init> '{params,returnObj,throwExp}' -v
 ```
 
+##### 输入中文/Unicode字符
+
+把中文/Unicode字符转为`\u`表示方法：
+
+```bash
+ognl '@java.lang.System@out.println("Hello \u4e2d\u6587")'
+```
 
 ##### java.lang.ClassFormatError: null、skywalking arthas 兼容使用