docs: function shift_formula_str(f, delta) {
  	return f.replace(crefregex, function($0, $1, $2, $3, $4, $5) {
  		return $1+($2=="$" ? $2+$3 : encode_col(decode_col($3)+delta.c))+($4=="$" ? $4+$5 : encode_row(decode_row($5) + delta.r));
  	});
  }