[#7710] update docs for v2.2.2

doc/main.md

 ---
-title: "Pinpoint 2.2.0"
-keywords: pinpoint release, 2.2.0
+title: "Pinpoint 2.2.2"
+keywords: pinpoint release, 2.2.2
 permalink: main.html
 sidebar: mydoc_sidebar
 ---
 
-## What's New in 2.2.0
+# What's New in 2.2.2
 
-[Check out updates on lastest stable release](https://naver.github.io/pinpoint/2.2.0/main.html)
+v2.2.2 is a bug fix release of 2.2.1
 
+There is a bug in the Reactor-netty plugin (v2.0.0 ~ 2.2.1) which inserts incorrect endPoint value.
+It only occurs in certain circumstances relating the high overload in Pinpoint-Collector
+To prevent this, it is recommended to upgrade to version 2.2.2 or higher when using the Reactor-netty plugin.
+  
 ## Upgrade consideration
 
 HBase compatibility table: