Flag support improvements

[Insire]

The flags that come with this lib are needlessly low quality.

Since they were taken from here which provides SVGs, there is no need to convert them to PNG and potentially loose quality for higher resolutions like 4k and above, when we can convert the data from the SVGs to native WPF objects aka paths or geometry instances.

There might also be some performance benefit of not having to deal with bitmaps.

PS: PackIconBase might be worth looking into.