fix: Missing cache for custom item models causing lags

src/main/kotlin/events/CustomItemModelEvent.kt

@@ -1,7 +1,10 @@
 package moe.nea.firmament.events
 
+import java.util.Optional
+import kotlin.jvm.optionals.getOrNull
 import net.minecraft.item.ItemStack
 import net.minecraft.util.Identifier
+import moe.nea.firmament.util.collections.WeakCache
 
 // TODO: assert an order on these events
 data class CustomItemModelEvent(
@@ -9,11 +12,17 @@ data class CustomItemModelEvent(
 	var overrideModel: Identifier? = null,
 ) : FirmamentEvent() {
 	companion object : FirmamentEventBus<CustomItemModelEvent>() {
+		val cache = WeakCache.memoize("ItemModelIdentifier", ::getModelIdentifier0)
+
 		@JvmStatic
 		fun getModelIdentifier(itemStack: ItemStack?): Identifier? {
-			// TODO: Re-add memoization and add an error / warning if the model does not exist
 			if (itemStack == null) return null
-			return publish(CustomItemModelEvent(itemStack)).overrideModel
+			return cache.invoke(itemStack).getOrNull()
+		}
+
+		fun getModelIdentifier0(itemStack: ItemStack): Optional<Identifier> {
+			// TODO: add an error / warning if the model does not exist
+			return Optional.ofNullable(publish(CustomItemModelEvent(itemStack)).overrideModel)
 		}
 	}