Custom file type registration example in README does not match the public API

[Vladipz]

The “Custom File Type Registration” example in the README does not compile against the current File.TypeChecker package (4.4.0).

The example uses:

public override string Name => "...";
public override string Extension => "...";
public override string MimeType => "...";
public override bool IsMatch(byte[] signature, Stream stream) => ...;

FileTypeValidator.RegisterType<MyCustomType>();
However, in the current API:
- FileType.Name, Extension, and MimeType are not virtual.
- FileType requires values through its protected constructor.
- IsMatch(...) does not exist.
- FileTypeValidator.RegisterType<T>() does not exist.
The documented approach that compiles is:
using FileTypeChecker;
using FileTypeChecker.Abstracts;

public sealed class MyCustomType : FileType
{
    public MyCustomType()
        : base(
            "My Custom Format",
            "application/x-mycustom",
            "mycustom",
            [0x4D, 0x59, 0x43, 0x54])
    {
    }
}

FileTypeValidator.RegisterCustomTypes(typeof(MyCustomType).Assembly);
Could the README be updated to match the public API, or could the documented API be restored?