Please consider implementing xoshiro256** (and/or xoshiro256+)

https://nullprogram.com/blog/2017/09/21/
"xoroshiro128+ fails PractRand very badly. [..] Since this article was published, its authors have supplanted it with xoshiro256**. It has essentially the same performance, but better statistical properties. xoshiro256** is now my preferred PRNG"

See also my https://github.com/JuliaLang/julia/issues/27614#issuecomment-454749117 for others to possibly implement (mostly Google's Randen based on AES, the one I list here would however be my first choice) and updated top comment there.

Start by reading the linked nullprogram article and the referenced Julia issue comment to understand the proposed xoshiro256** and xoshiro256+ options. No project files, tests, or entry points are named, so inspect RandomNumbers.jl's existing generator structure before deciding where this belongs; done means the requested generator is implemented and integrated consistently.

索引モデルが issue の本文から書いたものです。