update readme - button app

The title was causing the issue as there was no space between ## Screenshots. The images were also not shown for this reason. @RiyaGupta89 
I have changed it now.

Author: harshita2216

JAVASCRIPT BUTTON APP/README.md

@@ -31,8 +31,7 @@ node app.js
 ```
 - Have a look at the webapp.
 
-
-##Screenshots
+## Screenshots
 
 ![Demo1](public/images/challenge1.png)