doc: add header image and api.ai info

Author: spoeck

README.md

@@ -6,9 +6,13 @@
 
 A React-Native Bridge for the Google API AI SDK.
 
+<img src="header_img.png" alt="Header Image"/>
+
 Support for iOS 10+ and Android!
 
 
+[api.ai](https://api.ai) is a powerful tool for building delightful and natural conversational experiences. You can build chat and speech bots and may intergrate it in a lot of platform like twitter, facebook, slack, or alexa.
+
 ## Install
 
 Add react-native-api-ai and link it: