Disassembler: Add option to get register offsets

[Symbai]

For displacement and immediate we can get the offsets. For used registers we currently cannot. I'd like to request the possibility to retrieve the offsets for registers too (C#).

In my scenario I have an array of bytes where some registers are wildcarded. I need to know which register(s) was wildcarded from this array to deal with it later on.

namespace Iced.Intel {

	public readonly struct UsedRegister {

		public Register Register;
		public OpAccess Access;
++		public byte Offset;

	}
}