More Ammo Mod

Adds four custom ammo types to the shop loot pool as Rare items:

1. Black Hole Ammo: (Cost: 30, Sell: 15) Creates a temporary gravity well on impact that draws nearby targets in.
2. C4 Ammo: (Cost: 30, Sell: 15) Attaches a sticky C4 device to hit targets. Shooting them a second time detonates the charge, destroying all targets in a large radius.
3. Splitter Ammo: (Cost: 30, Sell: 15) Splits into two additional hitscan shots on target hit, dealing damage and drawing cyan visual tracers to the nearest targets.
4. Tesla Ammo: (Cost: 35, Sell: 17) Fires an electrical arc that automatically chains to multiple targets sequentially on impact.