Add ammo-category option to elem_type for choose-elem-button

[majoca]

I'm working on a mod that lets the player control various bonuses. It would be really helpful if I could create a choose-elem-button to select an ammo-category to set which category to apply damage/shooting speed bonuses to. The options could just appear exactly as they do in Factoriopedia.

Thanks!

[Rseding91]

Ok, I've added airborne-pollutant, ammo-category, quality, shortcut, space-connection, surface, and virtual-signal to choose elem types for 2.1.