Add support for exporting HEIF images

[Jeehut]

First, thank you very much for this tool, greatly appreciated. 👍

In Apples official guide on Doing Advanced Optimizationt Further Reduce Your Apps Size they suggest that we should "consider using the HEIF format for images".

For projects with many binary assets it would be great to switch from a PNG or JPG based approach to a HEIF based one. In the best case, we would even be able to provide the "Quality" percentage value so each developer can decide how much the image should be compressed.