Add option to modify the radar icon sizes

[AmjedAgabani]

Would be nice to be able to change the radar icon size on the HUD standalone from changing the entire HUD scaling

[drweissbrot]

Too niche of a use case for first class support in my opinion. You can do this with a theme, though I did notice that the radar icon sizes aren't CSS variables, which makes them a bit more effort to modify than should be the case (tracking in #146).

Thanks for the suggestion though! :)