Fix link in CONTRIBUTING.md
The documentation link for Airbnb ES5 styleguide is broken, this MR changes the link to the new document location. This changes because deprecation of it.
Do not update/delete: Banner broadcast message test data
Do not update/delete: Notification broadcast message test data
The documentation link for Airbnb ES5 styleguide is broken, this MR changes the link to the new document location. This changes because deprecation of it.