style(README):readme添加介绍 (#57)

Author: PurplePlanen

README.md

@@ -6,7 +6,7 @@ English | [简体中文](Docs/README.zh-CN.md)
     Moder
 </h1>
 
-Moder is a visual editor for HOI4 (Hearts of Iron IV)  that simplifies Mod development , Based on .NET Core and Avalonia, supports Windows and Linux platforms 
+Moder is a Cross-platform Visual editor for HOI4 (Hearts of Iron IV)  that simplifies Mod development , Based on .NET Core and Avalonia, supports Windows and Linux platforms 
 
 ## Runtime environment requirements