update readme

Author: joeeames

README.md

@@ -4,4 +4,6 @@ This course is up to date.
 To get started, clone the repo or download it
 
 npm install
-npm test
+npm test
+
+## IMPORTANT: do not try to run this code with "npm run" as it currently doesn't build. This isn't important to the course anyway, so just ignore that. Use "npm test" only.