docs: add a note in the readme about onProgress and onConversationResponse

readme.md

@@ -97,6 +97,8 @@ const response = await api.sendMessage('this is a timeout test', {
 })
 ```
 
+You can stream responses using the `onProgress` or `onConversationResponse` callbacks. See the [docs](./docs/classes/ChatGPTAPI.md) for more details.
+
 <details>
 <summary>Usage in CommonJS (Dynamic import)</summary>
 

src/chatgpt-api.ts

@@ -142,7 +142,7 @@ export class ChatGPTAPI {
         headers: {
           Authorization: `Bearer ${accessToken}`,
           'Content-Type': 'application/json',
-          'user-agent': this._userAgent
+          'User-Agent': this._userAgent
         },
         body: JSON.stringify(body),
         signal: abortSignal,