Update README.md (#326)

Added Community Extension

README.md

@@ -18,8 +18,7 @@ Contao developers to send notifications via their extensions.
 
 ### Community Extensions
 
-Currently, there are no known community extensions compatible with Notification Center 2.0. Feel free to create a
-Pull Request to add yours here!
+- [KlickTipp Gateway](https://extensions.contao.org/?p=fenepedia%2Fcontao-klicktipp-gateway) by [Fenepedia](https://www.fenepedia.de)
 
 ### Translating the Notification Center
 
@@ -51,4 +50,4 @@ Here is a short list of features you can expect from Notification Center Pro:
 * Provides custom simple tokens! You can conveniently create your own, custom Simple Tokens based on other tokens. This will allow you to be a lot more flexible by extracting partial information from other tokens, combining them or virtually doing whatever you can do with Twig with them.
 * Provides a "void" gateway: This gateway does not send any message at all. Instead, it just fakes delivery allowing for easier testing.
 
-💰 [Go get Notification Center Pro today!](https://extensions.terminal42.ch/p/nc-pro)
+💰 [Go get Notification Center Pro today!](https://extensions.terminal42.ch/p/nc-pro)