raise default secret size to 128

[termermc]

04:50 AM <termer> Elegantbeef, Gitea uses a 64 char TOTP secret
04:50 AM <termer> I'm thinking Nim OTP should have 64 as its default, not 32
04:51 AM <FromDiscord> <Elegantbeef> PR's welcome
04:51 AM <termer> All right
04:51 AM <FromDiscord> <Elegantbeef> Fuck it do 128 by default 😛

[ba0f3]

I'm not sure what value is the best :(

[beef331]

My uneducated view is that 128 bytes is only the size of array[16, int64] it's still relatively small. Remember this is just a default value. If someone wants they can always lower it. Ideally the size used accepts all common secrets, this size was the major concern I had implementing stackstrings here 😄 I do think 256 or 128 are very fair.