Add a link to GitHub notifications page

[iansu]

Both the logo link and the GitHub icon link to this repo. It would be nice if the GitHub one linked to https://github.com/notifications.

[mathpluscode]

This feature would be really nice!

[SpencerKaiser]

I'm on v4.2.0 and I don't see the button @manosim added via #473. Is there something special I need to do??