Implement app.dock.downloadFinished
Implement app.dock.downloadFinished

Make the Downloads folder dock icon "bounce" when a download is complete (macOS-only).

Resolves #1667
timborden/browser-laptop,luixxiul/browser-laptop,diasdavid/browser-laptop,diasdavid/browser-laptop,luixxiul/browser-laptop,luixxiul/browser-laptop,diasdavid/browser-laptop,timborden/browser-laptop,luixxiul/browser-laptop,timborden/browser-laptop,diasdavid/browser-laptop,timborden/browser-laptop