@Nonnull
    static VariableAmount baseWithOptionalAddition(double base, double addition, double chance) {
        return new OptionalAmount(base, chance, baseWithRandomAddition(base, addition));
    }
Creates a new variable about which has a base and a chance to apply a
random additional amount. The chance should be between zero and one with
a chance of one signifying that the additional amount will always be
applied. If the chance succeeds then the final amount will be the base
amount plus a random amount between zero (inclusive) and the additional
amount (exclusive). If the chance fails then the final amount will just
be the base value.

@param base The base value
@param addition The additional amount
@param chance The chance to apply the additional amount
@return A variable amount representation
helper/src/main/java/me/lucko/helper/random/VariableAmount.java