Vectorised sampling documentation

[treigerm]

The link in the README pointing towards more information about the vectorized implementation about static HMC points to a webpage which errors with 404:

It also supports vectorized sampling for static HMC and has been discussed in more detail in the documentation [here](https://turing.ml/dev/docs/library/advancedhmc/parallel_sampling).

I was looking for the following information: I think I remember reading somewhere that the implementation for static HMC is using coupled random numbers. However, I cannot find any information about that anymore so I'm not sure whether I am just misremembering.

[yebai]

Let's add an example utilising vectorised HMC to the docs