feat: support swagger configuration (#46)

example/main.go

@@ -25,7 +25,10 @@ import (
 func main() {
 	r := gin.New()
 
-	r.GET("/swagger/*any", ginSwagger.WrapHandler(swaggerFiles.Handler))
+	config := &ginSwagger.Config{
+		URL: "http://localhost:8080/swagger/doc.json", //The url pointing to API definition
+	}
+	r.GET("/swagger/*any", ginSwagger.WrapHandler(config, swaggerFiles.Handler))
 
 	r.Run()
 }