Added Readme

Assets/Plugins/StreamChat/Readme.txt

@@ -0,0 +1,21 @@
+About:
+Stream Chat Unity SDK allows for easy integration with Stream API Chat services - https://getstream.io/chat/
+
+GitHub repository:
+https://github.com/GetStream/stream-chat-unity
+
+First steps tutorial:
+https://getstream.io/chat/unity/tutorial/ 
+
+Documentation:
+https://getstream.io/chat/docs/unity/?language=unity 
+
+Plugin directory structure:
+- Config - sample config 
+- Core - the main logic of the Stream Chat SDK
+- Libs - dependencies of Stream Chat SDK, SDK depends on interfaces so you can provide you're own implementation
+- *SampleProject - example project
+- *Samples - code sample for example scenarios
+- *Tests - unit & integration tests
+
+* Directories prefixed with * above can be safely removed