salt_default_charset: add method for string salt with default charset

[acidelk]

I want calculate hash with default charset for salt.

[phxql]

Hi,

thanks for the PR. I plan to deprecate the methods accepting a String in the future, as they are not as secure as the char[] methods. Therefore I won't add any new methods accepting a password as a String.

[phxql]

But i see that there is a method with the signature

String hash(int iterations, int memory, int parallelism, char[] password, byte[] salt);

which uses the default UTF-8 encoding.

missing in Argon2Advanced.

[phxql]

I plan to deprecate all methods with accept a String password. Please do not add new ones.