Added support for Perplexity (#545)

Co-authored-by: Thorsten Sommer <mail@tsommer.org>

app/MindWork AI Studio/Provider/IResponseStreamLine.cs

@@ -12,5 +12,17 @@ public interface IResponseStreamLine
     /// Gets the content of the response line.
     /// </summary>
     /// <returns>The content of the response line.</returns>
-    public string GetContent();
+    public ContentStreamChunk GetContent();
+    
+    /// <summary>
+    /// Checks if the response line contains any sources.
+    /// </summary>
+    /// <returns>True when the response line contains sources, false otherwise.</returns>
+    public bool ContainsSources() => false;
+    
+    /// <summary>
+    /// Gets the sources of the response line.
+    /// </summary>
+    /// <returns>The sources of the response line.</returns>
+    public IList<ISource> GetSources() => [];
 }