Update API interface

Author: MaggieKimani1

test/Microsoft.OpenApi.Tests/PublicApi/PublicApi.approved.txt

@@ -448,6 +448,7 @@ namespace Microsoft.OpenApi.Models
         public const string Enum = "enum";
         public const string Example = "example";
         public const string Examples = "examples";
+        public const string ExamplesExtension = "x-examples";
         public const string ExclusiveMaximum = "exclusiveMaximum";
         public const string ExclusiveMinimum = "exclusiveMinimum";
         public const string Explode = "explode";