Add a page tutorial explaining how to write a sorter adapter

[Morwenn]

Writing an adapter isn't exactly an easy task, so having a tutorial with code would help, especially to avoid having to include a full example of how adapter_storage works in its documentation. Now the issue will be to find an example with a simple enough adapter which isn't 100% useless either.

[Morwenn]

Good example of a sorter adapter: one that shuffles the input before sorting the collection. The technique is mentioned in this article as a way to prevent Hyrum's law: with a sufficient number of users, someone will inevitably end up relying on observable yet non-guaranteed properties of algorithms, for example the order of elements that compare equivalent. A simple way to break tests relying on such a property is to randomize the order of elements prior to sorting, which can be desirable with a debug option.

A randomizing_adapter would therefore be a simple yet interesting example to demonstrate how to write a sorter adapter.