Wrap notification text

[jdujava]

Enable wrapping of notification_text. Also add small left/right margins.

Partially fixes pwmt/zathura#624.

[sebastinas]

This would need to be toogleable depending on the use of girara_notify. Not sure what the best approach is to make it generally useable.

[jdujava]

Is there currently some usecase where the text wrapping is undesirable? Focusing mainly on zathura, either the warning/error messages are short (so it doesn't make a difference), or I would rather see the whole message (copied text, PDF information, ...).

To be honest, I am not really confident that I would come up with a nice way to toggle it (and consistently apply necessary changes to other projects). Leaving it to someone more competent would be ideal :).

[sebastinas]

One approach to implement this would be to duplicate the notification area/code for a wrapped version and then check the uses of girara_notify where a wrapped version makes more sense.