Only number passwords accepted as best passwords

[bahramhasanov]

When user types passwords containing only numbers charsetBonus becomes 1.8, which is higher.

Need to add another control for numbers

if (RegExp(r'^[0-9]*$').hasMatch(password)) {
    charsetBonus = 0.5;
}

[fehernyul]

Or let us allow custom "estimateBruteforceStrength" function usage;