Update README.md

Author: longern

README.md

@@ -1,2 +1,14 @@
 # chatgpt-api-frontend
-Frontend of ChatGPT API
+Frontend of ChatGPT API, with an optional Cloudflare Worker backend to proxy requests and store tokens.
+
+## Features
+- [x] Chat with gpt-3.5-turbo model
+- [x] Stream HTTP responses
+- [x] Markdown support
+- [x] Code highlighting
+- [x] Save chat history
+- [x] Store token in backend or require user to provide it
+
+## Usage
+
+Open `index.html`. That's it!