add scroll to poll question container - mobile

bigbluebutton-html5/imports/ui/components/polling/styles.scss

@@ -52,6 +52,8 @@
     top: 50%;
     left: 50%;
     transform: translate(-50%, -50%);
+    max-height: 95%;
+    overflow-y: auto;
 
     [dir="rtl"] & {
       left: 50%;