Fixed IsDate property for nullable DateTime and DateTimeOffset

[ArtemDintecom]

This fix is ​​needed to make the following code work again:

if (p.Type.IsDate) {
    if (p.Type.IsNullable) {
        ...
    }
}

Also, instead of name, encodeURIComponent(String({name})) will now be generated again for DateTime?.

[AdaskoTheBeAsT]

hi thanks a lot for finding and fix! I will release this on weekend