Add support for \r line endings

[coffeefedora]

In the readme it is mentioned that \r only lines are not handled in the ReadLine() methods.

I am working with network HL7 data that uses \r only terminators, and the built in ReadLine() works with that.

this project is much much much faster than .net 8 standard StreamReader, and I would love to use this with the data.

If not willing to add it, is there an easy/efficient way I can manually emulate this behavior?

[coffeefedora]

I added a new function, and set a boolean to tell the class to use it.
probably better to do a "DetectCrOnly" type of check after loading the first like 1024 bytes into the buffer. I had trouble finding a place to insert that though.

[MethodImpl(MethodImplOptions.AggressiveInlining)]
static int IndexOfCR(ReadOnlySpan<byte> span, out int examined) {
  var indexOfCR = span.IndexOf((byte)'\r');
  if (indexOfCR == -1) {
     examined = span.Length - 1;
     return -1;
  }
  examined = indexOfCR;

  if(indexOfCR > 0 && span.Length>indexOfCR+1 && span[indexOfCR+1] == '\n') {
     examined++;
  }
  return indexOfCR;
}

this seems to handle \r only and \r\n.