Refactor response handling and add ToString method

Replaced `response.GetContent()` with `response` in `AskStreamAsync` method of `Application` class.
Added `ToString` method to `ChatGptResponse` class to return response content.

samples/ChatGptStreamConsole/Application.cs

@@ -1,5 +1,4 @@
 using ChatGptNet;
-using ChatGptNet.Extensions;
 
 namespace ChatGptStreamConsole;
 
@@ -44,7 +43,7 @@ public async Task ExecuteAsync()
 
                     await foreach (var response in responseStream)
                     {
-                        Console.Write(response.GetContent());
+                        Console.Write(response);
                         await Task.Delay(80);
                     }
 

src/ChatGptNet/Models/ChatGptResponse.cs

@@ -1,5 +1,6 @@
 using System.Diagnostics.CodeAnalysis;
 using System.Text.Json.Serialization;
+using ChatGptNet.Extensions;
 using ChatGptNet.Models.Common;
 using ChatGptNet.Models.Converters;
 
@@ -59,4 +60,11 @@ public class ChatGptResponse : Response
     /// <seealso cref="ChatGptChoice"/>
     /// <seealso cref="ChatGptChoice.IsFiltered"/>
     public bool IsContentFiltered => Choices.FirstOrDefault()?.IsFiltered ?? false;
+
+    /// <summary>
+    /// Gets the content of the response.
+    /// </summary>
+    /// <returns>The content of the response.</returns>
+    public override string? ToString()
+        => this.GetContent();
 }