Custom Spawns [Fabric]

Users can now modify all values related to mob's spawn category (e.g. monster, creature, ambient, etc.), including:
* Capacity (already customizable in previous releases)
* Peacefulness (whether mobs in this category are spawned as animals or monsters)
* Rare spawning (whether mobs in this category are spawned with the customizable rare spawn tick timer)
* Immediate Despawn Range (the distance at which mobs in this category immediately despawn, if not persistent)
* Despawn Start Range (the distance at which mobs start to have a change to despawn, typically 40 seconds, if not persistent)

Additionally the "Ticks between Passive Spawns" field has been renamed to indicate that any mobs with the above rare spawning option enabled will fall under this timer's constraint.