feat(core): add convenience operators for TextContent

Author: salty-flower

src/ModelContextProtocol.NET.Core/Models/Protocol/Shared/Content/TextContent.cs

@@ -1,7 +1,14 @@
+using System.Collections;
+using System.Runtime.CompilerServices;
+
 namespace ModelContextProtocol.NET.Core.Models.Protocol.Shared.Content;
 
 public record TextContent : Annotated
 {
     public string Type => "text";
     public required string Text { get; init; }
+
+    public static implicit operator Annotated[](TextContent textContent) => [textContent];
+
+    public static implicit operator TextContent(string text) => new TextContent { Text = text };
 }