Set <title> when viewing a beta notification #2555

When viewing a notification in the new beta notifications feature, the <title> of the window is just "Notifications". If you have several notifications open, it makes it difficult to find which one you were looking for.

https://github.com/notifications/beta/MDE4Ok5vdGlmaWNhdGlvblRocmVhZDQyMjY0MjY5Njo4MTE5NTQ=?query=is%3Aunread

<img width="246" alt="Screenshot of Google Chrome (20-11-19, 1-45-27 PM)" src="https://user-images.githubusercontent.com/811954/69199158-10a0d180-0b9c-11ea-84b0-74f46b54ee3d.png">

My suggestion is that the title of the window is updated to match the name of the issue/PR that you're looking at, like regular issues are.

https://github.com/tobias/dynapath/issues/12

<img width="394" alt="Screenshot of Google Chrome (20-11-19, 1-45-43 PM)" src="https://user-images.githubusercontent.com/811954/69199162-14ccef00-0b9c-11ea-9c4a-2419538a0788.png">

Perhaps you'd also add " - Notification" to the end of it to distinguish the tab from an issue view.

Example URL: https://github.com/notifications/beta/MDE4Ok5vdGlmaWNhdGlvblRocmVhZDQyMjY0MjY5Njo4MTE5NTQ=?query=is%3Aunread

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