Placeholder to get # of rewards in a crate

[Flavourized]

Suggestion is to add a placeholder which will return the number of possible rewards in the crate.

    rewards:
           - 'chance:(10), onOpen:(&a&lDR &8&l» &fa pile of dust..)'
           - 'chance:(50), cmd:(/ss give %player% skeleton 1), onOpen:(&a&lDR &8&l» &f1&7x &aSkeleton &7Spawner)'

This crate has 2 rewards, so the placeholder (maybe %crate_rewardcount%), will return 2.

Intention is to use this in the lore of the key/crate. The immediate issue i see with this is that if you change the amount of rewards in the crate, any keys/crates with a different/older amount of rewards will break, but i am sure you guys could find a workaround for this.

This is just a QoL feature.