normalize schema_url option

jsonform.gadget.js

@@ -799,7 +799,8 @@
         }
       }
       if (options.hasOwnProperty("schema_url")) {
-        z.schema_url = options.schema_url;
+        z.schema_url = (new URL(options.schema_url, window.location))
+          .toString();
       }
       if (options.value !== undefined) {
         z.value = JSON.stringify(options.value);