Custom Salt Length

[emelone16]

What are your thoughts on moving the variable defined here to an optional paramter in the Crypter constructor?

If we define the default to be the same as it currently is, this would not break backwards compatibility, but allow greater flexibility for users over how they use this library.

Happy to open a PR for this, but want to hear thoughts before I do the work.

EDIT: Learned more about this library and cryptography in general, realized that the salt is really the only length we can vary.

[pedropuppim]

I would like this

[MauriceButler]

Added in release v6.1.0