Fix scrolling on participants list

When using Firefox, the participants tab view requires its overflow to
be hidden to limit its size to the size of its parents. Otherwise, the
participants tab view grows to fit its children; if that happens then no
scroll bar is shown for the participants list, as the participants list
is tall enough to fit all its items (even if they are not visible
because they are in the overflow area). In Chromium, on the other hand,
the participants tab view size is always limited by its parents, no
matter if the overflow is hidden or not.

In a similar way, once the overflow is hidden the bottom padding added
to the participants list has to be added to its last item instead.
Firefox only takes into account the bottom padding in the participants
list when the list has not overflown the participants tab view; it needs
to be added to the last item to be taken into account also when the
participants list is taller than the participants tab view. Chromium, on
the other hand, always takes into account the padding, no matter if it
is added to the participants list or to its last item.

Signed-off-by: Daniel Calviño Sánchez <danxuliu@gmail.com>

css/style.scss

@@ -1044,10 +1044,14 @@ video {
 #app-sidebar #participantsTabView {
 	display: flex;
 	flex-direction: column;
+	overflow: hidden;
 }
 
 #app-sidebar .participantWithList {
 	overflow-y: auto;
+}
+
+#app-sidebar .participantWithList .participant:last-child {
 	/* Add room for the popovermenu on last user */
 	padding-bottom: 64px;
 }