Option to mute notifications

[timche]

Inspired by: https://github.com/sindresorhus/caprine#mute-desktop-notifications

[timche]

Added in v3.0.0-alpha.15.

[chrisma]

I would especially appreciate muting/disabling the download cancelled notifications (e.g. when bringing up the save dialog, seeing that the file is already present and canceling). I know the download was cancelled in this case: I clicked the button.

[timche]

Thanks for your feedback. I'll check if this can be made smarter.