Add fade-out after X time setting

[Rob--W]

Feedback from user (Jeremy) via the Chrome Web Store:

notification persist until interacted with. maybe good for some, but my preference would be a growl that goes away after a little time. perhaps this could be a setting?

[kav2k]

This does not apply to chrome.notifications, they cannot stay shown indefinitely anyway and it's managed by Chrome itself.

With webkitNotification removed, this is still relevant if rewritten for Notification. Are you going to do it, or are you going to switch to chrome.notifications as primary?

[Rob--W]

I reckon that automatic dismissal can be implemented by setTimeout and chrome.notifications.remove - https://developer.chrome.com/extensions/notifications#method-clear

[kav2k]

There's hardly a need for that: notifications will automatically fade into the tray icon after a few seconds. priority can make it longer, but not indefinitely long.

From UX perspective, it's not good to clear the notification on timeout: they are supposed to stay in the tray icon list until interacted with.

[kav2k]

It's a bit of an awkward spot right now. With #22, you have the "default" no-persistence Chrome notifications, and an option (that only works in Chrome 50+, despite being shown to everyone) to enable persistence.

Wouldn't it confuse even further if the extension had a controllable timeout that only works in Chrome 50+? Is it really warranted to fine-tune this duration?

[Rob--W]

@kav2k At some point everyone should be using 50+, so this is fine. I see no problem with offering the ability to set the interval.

It's even possible to feature-detect it and disable the button in the absence of it: e8f248954585bce042990b7102f4f166ff52b0a4