Unify push notification UX guidelines

[gauntface]

From @dandv

We have two documents on good push notification UX:

What Makes a Good Notification? on Web Fundamentals
and
Best Practices for Push Notifications Permissions UX (strangely, a Google Doc)

Would it make sense to bring the latter under /web and/or merge it into the former?

CC @owencm, @jpmedley

[ithinkihaveacat]

Related: the Material Design notification guidelines.

[beverloo]

Missing links:

• What Makes a Good Notification
• Best Practices for Push Notifications Permissions UX

There's also the Android UX guidelines.

[gauntface]

When I wrote up the original permission UX, I had Owens doc in mind.

Is there a particular bit I'm missing here?