Change RequestOptions.Stop to be a string array

Fixes #52

src/Models/RequestOptions.cs

@@ -110,7 +110,7 @@ public partial class RequestOptions
 	/// </summary>
 	[JsonPropertyName("stop")]
 	[JsonIgnore(Condition = JsonIgnoreCondition.WhenWritingNull)]
-	public string? Stop { get; set; }
+	public string[]? Stop { get; set; }
 
 	/// <summary>
 	/// Tail free sampling is used to reduce the impact of less probable