feat: add models for streaming messages

src/AnthropicClient/Models/ContentStopEventData.cs

@@ -0,0 +1,18 @@
+using System.Text.Json.Serialization;
+
+namespace AnthropicClient.Models;
+
+public class ContentStopEventData : EventData
+{
+  public int Index { get; init; }
+
+  [JsonConstructor]
+  internal ContentStopEventData() : base(EventType.ContentBlockStop)
+  {
+  }
+
+  public ContentStopEventData(int index) : base(EventType.ContentBlockStop)
+  {
+    Index = index;
+  }
+}