Update README.md

Author: hasanbayatme

README.md

@@ -9,6 +9,7 @@ We have collected most scripts from external sources like Unity Communities (For
 - [Scripts/Editor/](https://github.com/UnityCommunity/UnityLibrary/tree/master/Scripts/Editor) : Editor related scripts.
 - [Shaders/](https://github.com/UnityCommunity/UnityLibrary/tree/master/Shaders) : Ready-to-use shaders.
 - [ScriptTemplates/](https://github.com/UnityCommunity/UnityLibrary/tree/master/ScriptTemplates) : Contains ready-to-use script templates.
+- [External/](https://github.com/UnityCommunity/UnityLibrary/tree/master/External) : External libaries, scripts and utilities that are related to unity.
 
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