Performs a d20 roll. Options can modify the number of D20s rolled:

• :advantage - Rolls 2d20 and takes the max
• :disadvantage - Rolls 2d20 and takes the min

Normal behavior is a 1d20.

@spec roll(
  String.t() | Srd.Dice.Expr.t(),
  keyword()
) :: Srd.Dice.Roll.t()

Roll a dice expression and return an immutable Srd.Dice.Roll.

Takes a notation string or a parsed Srd.Dice.Expr. The :reduce option names how the dice are combined before the modifier is added. The default is :sum

iex> Srd.Dice.roll("2d6+3")
%Srd.Dice.Roll{count: 2, sides: 6, modifier: 3, dice: [4, 5], reduce: :sum, total: 12}

iex> Srd.Dice.roll("2d20", reduce: :max)   # advantage
%Srd.Dice.Roll{count: 2, sides: 20, modifier: 0, dice: [7, 18], reduce: :max, total: 18}