polymc: include qt6-qtsvg and qt6-qtimageformats as dependencies
PolyMC mostly uses SVG for its icons.
qt6-qtsvg the icon theme will be broken.
Most other distro packages have
libQt6Svg.so as a runtime dependency.
qt6-qtimageformats should either be a runtime or optional runtime dependency, as some features (such as the modpack/mod browser) may load images in formats like WebP.