Add custom texture pack support

src/main/kotlin/moe/nea/firmament/events/CustomItemModelEvent.kt

@@ -0,0 +1,41 @@
+package moe.nea.firmament.events
+
+import java.util.*
+import net.minecraft.client.render.model.BakedModel
+import net.minecraft.client.render.model.BakedModelManager
+import net.minecraft.client.util.ModelIdentifier
+import net.minecraft.item.ItemStack
+
+data class CustomItemModelEvent(
+    val itemStack: ItemStack,
+    var overrideModel: ModelIdentifier? = null,
+) : FirmamentEvent() {
+    companion object : FirmamentEventBus<CustomItemModelEvent>() {
+        private val cache = IdentityHashMap<ItemStack?, Any>()
+        private val sentinelNull = Object()
+
+        fun clearCache() {
+            cache.clear()
+        }
+
+        @JvmStatic
+        fun getModelIdentifier(itemStack: ItemStack?): ModelIdentifier? {
+            if (itemStack == null) return null
+            return publish(CustomItemModelEvent(itemStack)).overrideModel
+        }
+
+        @JvmStatic
+        fun getModel(itemStack: ItemStack?, thing: BakedModelManager): BakedModel? {
+            if (itemStack == null) return null
+            val cachedValue = cache.getOrPut(itemStack) {
+                val modelId = getModelIdentifier(itemStack) ?: return@getOrPut sentinelNull
+                val bakedModel = thing.getModel(modelId)
+                if (bakedModel === thing.missingModel) return@getOrPut sentinelNull
+                bakedModel
+            }
+            if (cachedValue === sentinelNull)
+                return null
+            return cachedValue as BakedModel
+        }
+    }
+}