Add custom global textures

src/main/kotlin/moe/nea/firmament/features/texturepack/CustomModelOverrideParser.kt

@@ -7,9 +7,27 @@
 package moe.nea.firmament.features.texturepack
 
 import com.google.gson.JsonObject
+import kotlinx.serialization.KSerializer
+import kotlinx.serialization.descriptors.SerialDescriptor
+import kotlinx.serialization.encoding.Decoder
+import kotlinx.serialization.encoding.Encoder
 import net.minecraft.util.Identifier
 
 object CustomModelOverrideParser {
+    object FirmamentRootPredicateSerializer : KSerializer<FirmamentModelPredicate> {
+        val delegateSerializer = kotlinx.serialization.json.JsonObject.serializer()
+        override val descriptor: SerialDescriptor
+            get() = SerialDescriptor("FirmamentModelRootPredicate", delegateSerializer.descriptor)
+
+        override fun deserialize(decoder: Decoder): FirmamentModelPredicate {
+            val json = decoder.decodeSerializableValue(delegateSerializer).intoGson() as JsonObject
+            return AndPredicate(parsePredicates(json).toTypedArray())
+        }
+
+        override fun serialize(encoder: Encoder, value: FirmamentModelPredicate) {
+            TODO("Cannot serialize firmament predicates")
+        }
+    }
 
     val predicateParsers = mutableMapOf<Identifier, FirmamentModelPredicateParser>()