Feature request: Allow for globally changing size & used alphabet

[BlackBearFTW]

Hi,

It would be great if Nanoid allows for settings to be set globally, like the size and alphabet, something like;

Nanoid.Defaults.Size = 100 & Nanoid.Defaults.Alphabet = " ".

This would allow for less configuring, for example I use Nanoid.Alphabets.LettersAndDigits everywhere and now I have to pass that in each time I want to generate a Nanoid.