Add support for random ranges for repeats/event (e.g: "num_repeats: 5-10")

[hopperelec]

https://github.com/HopperElec/RandomEventsPlugin/blob/4276fb67c143e75cfa95a45308aa05984d4a490f/src/main/java/uk/co/hopperelec/mc/randomevents/specialitems/functionality/SpecialItemRandomEvent.java#L33-L37