Make indent configurable

Nbt/Serialization/SNbt.cs

@@ -17,6 +17,7 @@ public static class SNbt
         public static readonly SerializerOptions Default = new();
 
         public SerializationStyle Style { get; init; } = SerializationStyle.Compact;
+        public string Indent { get; init; } = "  ";
         public bool AlwaysQuoteTagNames { get; init; } = false;
         // public bool AlwaysQuoteStringTags { get; init; } = false;
     }
@@ -101,7 +102,7 @@ public static class SNbt
         {
             for (var i = 0u; i < depth; i++)
             {
-                writer.Write("  ");
+                writer.Write(options.Indent);
             }
         }