Tutorial: using tskit for (statistical) analysis

[hyanwong]

The msprime main docs page says "The tskit tutorials site contains in-depth tutorials on different aspects of msprime simulations as well as how to analyse simulated tskit tree sequences.". I think it might be useful to have an "analysis" tut, although much of the material is covered in https://tskit.dev/tskit/docs/stable/tutorial.html#computing-statistics, so perhaps we want to move that (and https://tskit.dev/tskit/docs/stable/tutorial.html#calculating-ld) over to the tutorials site? See tskit-dev/tskit#1121