Add item id generator for 1.20.3 -> 1.20.5 (#16)

src/main/java/com/viaversion/mappingsgenerator/extra/ItemIds1_20_3.java

@@ -0,0 +1,43 @@
+/*
+ * This file is part of ViaVersion Mappings - https://github.com/ViaVersion/Mappings
+ * Copyright (C) 2023 Nassim Jahnke
+ * Copyright (C) 2023 ViaVersion and contributors
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+package com.viaversion.mappingsgenerator.extra;
+
+import com.github.steveice10.opennbt.tag.builtin.CompoundTag;
+import com.github.steveice10.opennbt.tag.builtin.ListTag;
+import com.github.steveice10.opennbt.tag.builtin.StringTag;
+import com.google.gson.JsonArray;
+import com.google.gson.JsonElement;
+import com.viaversion.mappingsgenerator.MappingsLoader;
+import com.viaversion.mappingsgenerator.MappingsOptimizer;
+
+import java.io.IOException;
+
+public final class ItemIds1_20_3 {
+
+    public static void main(final String[] args) throws IOException {
+        final JsonArray items = MappingsLoader.load("mapping-1.20.3.json").getAsJsonArray("items");
+        final CompoundTag tag = new CompoundTag();
+        final ListTag<StringTag> list = new ListTag<>(StringTag.class);
+        for (final JsonElement element : items) {
+            list.add(new StringTag(element.getAsString()));
+        }
+        tag.put("items", list);
+        MappingsOptimizer.write(tag, MappingsOptimizer.OUTPUT_DIR.resolve("itemIds-1.20.3.nbt"));
+    }
+}