Improve Push Notifications Experience

[vinaypuppal]

• Make UX better while subscribing
• Use push actions in push notification to bookmark or open url without opening app

[vinaypuppal]

• Remove subscription toggle on browser's that don't support service workers.
• When user deny's permission at first and later want to subscribe present logic is not working, so refactor for this case.

[duttakapil]

Push notifications not working in Opera :

OS : Windows 10 (lated/updated)
Browser : Opera (Latest)