Update add-app.md

i just wand to test it

docs/Store/add-app.md

@@ -1,5 +1,5 @@
 # Add an App
-
+https://www.nvidia.com/en-us/geforce-now/
 First, please make sure the site accepts IFrame. You can check this by inserting the sites URL into this: [IFrame checker](https://www.tinywebgallery.com/blog/advanced-iframe/free-iframe-checker)
 
 ## Ways to add an app to the store