New helper tool(s) for cross-platform application icons

When it comes to creating application icons, cross-platform applications need to provide different sets of icon resources for each platform that the app supports. Sometimes, this involves manually duplicating data – for example, a 48x48 image could form one of the standard sized items in an *.ico file for Windows, while also forming the MDPI launcher icon for Android.

Qt Creator currently has a tool to auto-generate multiple icon sizes from a single "master" image (see https://doc.qt.io/qtcreator/creator-deploying-android.html#icons-and-splash-screens ). It would be nice to have a cross-platform version of this, where the developer can supply a "master" image (or a few different ones to cover a range of resolutions) as part of the project, and the build system auto-generates other sizes and packs them up for the relevant platforms as configured.