WIP: RFC: Revamp list page

This is a total revamp of the pages describing listviews and intented to replace both.

It deviates a bit from the rest of the HIG since it focusses more on the actual implementation using Kirigami than on the design details. This is better IMO since it is less likely to change even when we decide to change our design and gives people an actual guide for implementation. It does not cover the full feature set of the Kirigami API, that is better left to its API docs. Nevertheless it tries to elaborate design decisions and discusses when to use certain thing.

It is missing a lot of images and could be expanded a bit, but first I'd like to get some feedback on the general direction