Welcome to Image Shrinker 1.6.1 🍕
Starting with MacOS 10.14.5, all signed applications by ‘new’ developers will need to be notarized or they will trigger Apple’s Gatekeeper software and prevent users from installing the app. That means that aside from signing Image Shrinker, I will need to notarize it as well.
Thanks to Kilian Valkhof for giving me all the hints: https://kilianvalkhof.com/2019/electron/notarizing-your-electron-application/