Support for Mac native notifications

[youngxhui]

now, notifications in mac like this

but other browser, notifiactions is better in mac.

testing website: https://www.bennish.net/web-notifications.html

[CutterKnife]

Set alerts.useSystemBackend to true.

[youngxhui]

thanks

[erifneerg]

for those clueless go to about:config

this also should be just set to true by default.