MAPG-235 go back to start button added to the end of the challenge

public/static/css/game.css

@@ -153,6 +153,10 @@
     z-index: 2;
 }
 
+#goToStart {
+    display: none;
+}
+
 @media screen and (max-width: 599px) {
     #mapName {
         display: none;