Parsing and generation of Forsyth-Edwards Notation (FEN) strings.
parse/1 turns a FEN string into board, turn, castling, en-passant and clock
fields consumed by Echecs.Game.new/1; to_string/1 serializes a game back.
Squares follow the Echecs.Board 0 = a8 convention.
Summary
Types
@type fen() :: String.t()