Initial sync

Test/StreamMark.cs

@@ -0,0 +1,9 @@
+namespace Nbt.Test;
+
+public readonly struct StreamMark(Stream stream) : IDisposable
+{
+    private readonly Stream _stream = stream;
+    private readonly long _pos = stream.Position;
+
+    public void Dispose() => _stream.Position = _pos;
+}