docs(who-uses): add remberg.de

Author: cwoebker

content/discover/who-uses.json

@@ -278,6 +278,7 @@
     "https://e-design.ca",
     "https://growthmill.com",
     "https://tarken.com.br",
-    "https://remato.com"
+    "https://remato.com",
+    "https://remberg.de/en"
   ]
 }