v1.17.1 - maintenance release

This release mainly fixes compilation and build issues for various platforms.

Other changes:

• fix issue of loading images with premultiplied alpha channel,
• correctly set compatible_version for macOS dylib builds,
• fix loading HDR PNGs, but encoding them as 8-bit SDR,
• fix saving AVIF with alpha using the SVT-AV1 encoder,
• @kleisauke has modernized the JS wrapper (thanks!).