Add radwege-check to "Wo uses it" (#113)

* Add radwege-check to "Wo uses it"

* Update who-use-it.md

Describe type of data; add Github link

Author: tordans

docs/who-use-it.md

@@ -20,6 +20,8 @@ The short list of projects using Itemsjs for powering faceted search:
 
 - Nobel Laureats - https://www.nobelprize.ru (AMP Frontend)
 
+- Radwege-Check.de - https://bikelane-safetycheck.net/ (survey results, React/Gatsby, [Source](https://github.com/FixMyBerlin/fixmy.safetycheck))
+
 And portfolios:
 
 - https://www.anand-iyer.com/publications/