Use SVGs where appropriate

[nelson137]

Use SVGs where it makes the most sense such as the end-game icons (winner crown, and white and black loser #) and arrows (#6).

Currently, SVGs are difficult in bevy. There is no official support for them and while there is a proof of concept crate bevy_prototype_lyon, it doesn't work well with bevy_ui.

SVGs can be used in bevy, but I haven't found a way to make them work properly with UI entities. It is possible to have them but would require systems that manually reposition the SVGs each frame after the UI systems run (just UiSystem::Flex?).

This might be blocked until bevy gets its new UI framework and/or gets proper SVG support.