add london rust user group

Author: booyaa

data/supporters.json

@@ -1683,6 +1683,19 @@
           "email": "[email protected]"
         }
       ]
+    },
+    {
+      "name": "London Rust User Group",
+      "city": "London",
+      "country": "United Kingdom",
+      "link": "http://meetup.com/Rust-London-User-Group/",
+      "contacts": [
+        {
+          "name": "Mark Sta Ana",
+          "twitter": "booyaa",
+          "email": "[email protected]"
+        }
+      ]
     }
   ]
 }