Function matchIconSize
Check if matchSize belongs to subdir's size range.
Example
auto fixed = IconSubDir(32, IconSubDir .Type .Fixed);
assert(matchIconSize(fixed, fixed .size()));
assert(!matchIconSize(fixed, fixed .size() - 2));
auto threshold = IconSubDir(32, IconSubDir .Type .Threshold, "", 0, 0, 5);
assert(matchIconSize(threshold, threshold .size() + threshold .threshold()));
assert(matchIconSize(threshold, threshold .size() - threshold .threshold()));
assert(!matchIconSize(threshold, threshold .size() + threshold .threshold() + 1));
assert(!matchIconSize(threshold, threshold .size() - threshold .threshold() - 1));
auto scalable = IconSubDir(32, IconSubDir .Type .Scalable, "", 24, 48);
assert(matchIconSize(scalable, scalable .minSize()));
assert(matchIconSize(scalable, scalable .maxSize()));
assert(!matchIconSize(scalable, scalable .minSize() - 1));
assert(!matchIconSize(scalable, scalable .maxSize() + 1));