block shipscope alerts from notification center.

@mlocher It seems like numbers would be better than bullets in this PR, but they looked a little weird. Is there a good way to make an ordered list in these docs? I couldn't find any examples.



Provided steps to disable Shipscope alerts so they don't fill up the
Chrome Notification Center.
It was actually @AlexTi writing the text, I just pushed for releasing it ;)