Create up-to-date docs about Bisq 2

There is no up to date documentation about Bisq 2.
The [readme](https://github.com/bisq-network/bisq2/blob/main/README.md) is outdated as well as the linked pages from there as well as the various discussion or proposal pages.

Here a list of documents and scopes which would be good to cover:
- High level overview about goals and motivation (similar and updated to the links in the readme file)
- High level overview about the concepts from user point of view (options and features) and from architecture (modules, layers)
- Overview about the core modules and layers: P2P network, multiple mix network support, multiple wallet support, identity concept, reputation system, protocol execution framework, oracle nodes,...
- Overview about concepts how to implement a mobile app for Bisq Easy (Android vs. iOS)
- Overview about the infrastructure of nodes and how it connects to Bisq 1 and the DAO (bridge nodes), APIs, Webinterface for selfhosted node projects, Mobile app
- Roadmap for protocols we have in mind (new ideas about LN-> L-BTC -> LN is not documented at all yet)
- Dev docs, how to setup, run Bisq 2, code styles and concepts

Where it makes sense a graphical overview would be good as well. As most parts are quite complex, I think to split it in a high level overview to get a quick idea and a detail spec would be good.

Start by auditing README.md and the pages it links to, then compare them with the discussion and proposal pages mentioned in the issue. Done should include an agreed structure for high-level and detailed Bisq 2 documentation covering the listed concepts, infrastructure, roadmap, mobile app guidance, and developer setup.

Written by the indexing model from the issue text.