PSA: discovery and Syncthing in a container: use docker host networking

[bt90]

v2: Docker host network mode as default

This is more of a documentation thing if anything and not strictly tied to v2. But people will have a closer look at their deployments with v2 and I hope we can guide some of them towards a better setup. We already have a documentation section that covers the host networking mode and how it improves discovery: Can we just adapt our CLI and Compose examples in the top section to also use host network mode by default? Most people tend to simply copy&paste the very first Compose bits and end up…

Guess I need to finally get this done