IBBoard

There may be a bug in this that I need to track down. I've not worked out when. But sometimes it seems to use some default settings for the blur....

After running this for a while, it's not 100% consistent, but it sometimes seems to go for a heavy blur, and it seems to be when I have to wake...

I've not put in logging to chase it down yet. You could merge it if you want, because I think "mostly gets the right dimming/blur" is better than "rarely gets...

If you want a version for Gnome support then merge this and I'll work on the the occasional default blur levels separately.

There's already a ticket for this with a command-line workaround - https://github.com/johnfactotum/foliate/issues/1196#issuecomment-2438425213