PWA setup along with routes for storing subscriptions and sending push notifications

[DhananjayPurohit]

This PR supports PWA setup along with routes for storing subscriptions and sending push notifications.

How it works:-

1. After cloning and following the installation steps (no change in installation steps for this PR), visiting http://localhost:4000 would ask permission to show notifications.
2. Hitting "Allow" would send subscription object to /webpush/notifications/subscribe through a POST request that would be stored in PostgreSQL database inside subscriptions table.
3. Hitting the URL http://localhost:4000/webpush/notifications/payload?title=Orcasound&body=Test%20push%20notification would send a GET request with a payload that would send push notifications to all the stored subscription objects.

[paulcretu]

@DhananjayPurohit I converted this PR into a draft because the v3 redesign is still underway. I don't think we'll be merging this PR in until that's completed, and you'll probably have to fix some conflicts at that point anyway.

[DhananjayPurohit]

@DhananjayPurohit I converted this PR into a draft because the v3 redesign is still underway. I don't think we'll be merging this PR in until that's completed, and you'll probably have to fix some conflicts at that point anyway.

I would love to make changes in this PR after progress on v3.

[paulcretu]

@DhananjayPurohit v3 was released a few months ago! We now have email notifications but no web push notifications. Still interested in revisiting this PR? Otherwise I would close it as it probably needs almost a complete rewrite

[DhananjayPurohit]

Cool. I will create a new PR after rewriting the logic for web push notifications on the latest version (v3). Thanks.