Show a desktop notification when done processing in the background

[nekohayo]

I often throw a dozen of PNG images at Yoga to optimize, but encoding often takes a very long time. Usually I either switch away to another application and then forget to come back to Yoga's results, or I just sit in front of Yoga, which is improductive.

It would be nice if Yoga could emit a "transient" freedesktop notification just to visually let me know when it's done, so that I can go back to it from whatever else I was doing in another application, if needed.