Ammo tracking is broken

[jonatanhedborg]

When attempting to fire a weapon a weapon with ammo a second time, you tte the " ... is out of ammo!" error. At a glance this might be because the check uses ammo.value instead of ammo.current?

I'd create a PR but I can't get the project to build (missing foundryconfig.json I think?)

As an aside, I'd like to thank you for setting this up! I was looking for a SWN system one day and then the next it was just there :)