fix: load own spec with relative path

Without this the spec won't render when the generator is exposed on a sub path

Author: fgreinacher

modules/swagger-generator/src/main/webapp/index.html

@@ -73,7 +73,7 @@
 window.onload = function() {
   // Build a system
   const ui = SwaggerUIBundle({
-    url: "/api/swagger.json",
+    url: "./api/swagger.json",
     dom_id: '#swagger-ui',
     presets: [
       SwaggerUIBundle.presets.apis,