Implement StringTag, run autofix

lib/nbt/impl/ByteArrayTag.dart

@@ -2,7 +2,7 @@ import 'package:libac_flutter/nbt/Stream.dart';
 import 'package:libac_flutter/nbt/Tag.dart';
 
 class ByteArrayTag extends Tag {
-  List<int> _value = [];
+  final List<int> _value = [];
 
   ByteArrayTag();
 

lib/nbt/impl/CompoundTag.dart

@@ -5,7 +5,7 @@ class CompoundTag extends Tag {
   late final Map<String, Tag> _value;
 
   CompoundTag() {
-    _value = new Map();
+    _value = <String, Tag>{};
   }
 
   @override
@@ -43,9 +43,9 @@ class CompoundTag extends Tag {
   }
 
   Tag? get(String name) {
-    if (contains(name))
+    if (contains(name)) {
       return _value[name] as Tag;
-    else {
+    } else {
       // Does not exist!
       return null;
     }

lib/nbt/impl/IntArrayTag.dart

@@ -2,7 +2,7 @@ import 'package:libac_flutter/nbt/Stream.dart';
 import 'package:libac_flutter/nbt/Tag.dart';
 
 class IntArrayTag extends Tag {
-  List<int> _value = [];
+  final List<int> _value = [];
   IntArrayTag();
 
   IntArrayTag._(List<int> value) {

lib/nbt/impl/LongArrayTag.dart

@@ -2,7 +2,7 @@ import 'package:libac_flutter/nbt/Stream.dart';
 import 'package:libac_flutter/nbt/Tag.dart';
 
 class LongArrayTag extends Tag {
-  List<int> _value = [];
+  final List<int> _value = [];
   LongArrayTag();
 
   LongArrayTag._(List<int> lst) {

lib/nbt/impl/StringTag.dart

@@ -1,18 +1,26 @@
 import 'package:libac_flutter/nbt/Stream.dart';
 import 'package:libac_flutter/nbt/Tag.dart';
 
-class TagString extends Tag {
-  final String value;
-  TagString({required this.value});
+class StringTag extends Tag {
+  String _value = "";
+  StringTag();
+
+  StringTag._(String str) {
+    _value = str;
+  }
+
+  static StringTag valueOf(String str) {
+    return StringTag._(str);
+  }
 
   @override
   void readValue(ByteLayer data) {
-    // TODO: implement readValue
+    _value = data.readString();
   }
 
   @override
   void writeValue(ByteLayer data) {
-    // TODO: implement writeValue
+    data.writeString(_value);
   }
 
   @override