Implement basic NBT PODO

lib/nbt/Tag.dart

@@ -0,0 +1,35 @@
+import 'Stream.dart';
+
+enum TagType {
+  End(0),
+  Byte(1),
+  Short(2),
+  Int(3),
+  Long(4),
+  Float(5),
+  Double(6),
+  ByteArray(7),
+  String(8),
+  List(9),
+  Compound(10),
+  IntArray(11),
+  LongArray(12);
+
+  final int byte;
+  const TagType(this.byte);
+}
+
+abstract class Tag {
+  late TagType type;
+
+  int getType() {
+    return type.byte;
+  }
+
+  TagType getTagType() {
+    return type;
+  }
+
+  void writeValue(ByteLayer data);
+  void readValue(ByteLayer data);
+}