Option to select a default icon to be used as a favicon when no favicon is found.

[albertoloscerritos]

Hi, thanks for the awesome plugin.
I think it would be a great idea if we could select a default icon to be used when no favicon is returned or found.

Like in this case, it would be useful to able to add some icon, so that it has the same aesthetic as the other links.
These are my settings

I hope you like the idea. Thanks.