Add a class/module method to read in a .dict file to a SequenceDictionary

[nh13]

def read_seq_dict(path: Path) -> SequenceDictionary:
    with fgpyo.sam.reader(path, file_type=sam.SamFileType.SAM) as fh:
        seq_dict: SequenceDictionary = SequenceDictionary.from_sam(header=fh.header)
        return seq_dict