visualise Berlin bicycle counters

[Berlin has set up a few bicycle detectors across the city](https://www.berlin.de/senuvk/verkehr/lenkung/vlb/de/radzaehlungen.shtml). They also [have a map](https://www.berlin.de/senuvk/verkehr/lenkung/vlb/de/karte.shtml), but it's not very intuitive, iFrame-based and doesn't really work on mobile devices.

We can do better. **Let's make visualise the data in a meaningful way, on a mobile-friendly website.** We may also create multiple forms of presentation for different purposes, or compare it to other cities.

*Note*: I'm not sure if the data is [open](https://opendefinition.org). We may want to visualise is anyways (to show what would be possible if it was open) or talk to the administration.