adds header

api/main.cpp

@@ -1,6 +1,5 @@
 #include <crow.h>
 #include <crow/app.h>
-#include <fstream>
 
 #include "isbn-interaction.h"
 
@@ -24,6 +23,8 @@ int main()
 	CROW_ROUTE(app, "/add/<string>")
 		([](std::string isbn)
 		 {
+		 	crow::response response(add_new_book(isbn));
+			response.add_header("Access-Control-Allow-Origin", "*");
 		 	return crow::response(add_new_book(isbn));
 		 });