Build: Add redirect to fix 404 at http://api.jquery.com/extending-ajax

Follows-up 58373d3.
Ref jquery#84.

Author: Krinkle

Gruntfile.js

@@ -43,4 +43,6 @@ grunt.registerTask( "build", [
 	"build-xml-full"
 ]);
 
+grunt.registerTask( "deploy", [ "wordpress-deploy", "deploy-redirects" ] );
+
 };

redirects.json

@@ -1,3 +1,4 @@
 {
-  "/api/": "/resources/api.xml"
+  "/api/": "/resources/api.xml",
+  "/extending-ajax/": "/jQuery.ajax/#extending-ajax"
 }