Updated README.md

Author: ArtemAnoshin

README.md

@@ -5,4 +5,8 @@ Xenforo2 anti-spam extension.
 ## How to install
 
 1) Copy CleanTalk folder to your <xenforo root directory>/src/Addons
-2) Go to ACP->Addons->Install
+2) Go to ACP->Addons->Install
+
+## Requirements
+
+* CleanTalk account https://cleantalk.org/register?product=anti-spam