Charge stat for Item (#4392)

* Stat.discharge, discharge

* Update Items.java

* item.discharge

* full container = somewhat more than 4 full batteries

* Stat.discharge

* stat.discharge = Discharge

* Update core/src/mindustry/type/Item.java

Co-authored-by: Antsiferov Andrew <summet.dev@gmail.com>

* removed dis

* oops

* unit zap

Co-authored-by: Antsiferov Andrew <summet.dev@gmail.com>

core/src/mindustry/world/meta/Stat.java

@@ -15,6 +15,7 @@ public enum Stat{
     explosiveness,
     flammability,
     radioactivity,
+    charge,
     heatCapacity,
     viscosity,
     temperature,