Add funnel from Trustroots.org to app or partners

[shuesken]

We need to actually tell Trustroots.org users about Nostroots and the app and partners. Some of them we can reach with a newsletter. The most engaged users, however, are the ones currently looking for hosting. To reach them, we need to introduce some marketing on the Trustroots.org website. Ideally this marketing can be tailored to users who are in a particular geographic location (so we can focus on Berlin first), in particular circles (so we can show most interesting partner orgs), and allows for some kind of tracking of how many people actually follow that funnel.

The main challenge here is that the Trustroots.org codebase is unpleasant to work with and any changes come with the risk of introducing bugs and also the risk of burning out the relevant developers, who are by and large the same people working on this project. It is important to make changes that are as minimal and decoupled and defensive as possible.

There is code already for introducing a banner, which would be untargeted. This is the safest option.

We also store the location of the search map and the applied filter (=circles) in local storage. So it may be possible to add a footer component that reads from this storage and allows for better targeting while not interacting with the rest of the code too much. However, visual components can easily break UI.

Tracking how many people click is likely the easiest part. I imagine we can run a link forwarder at link.trustroots.org to handle this.