Use double angle brackets as occupants toggle icon

updates #1072

src/converse-muc-views.js

@@ -697,11 +697,15 @@
                 setOccupantsVisibility () {
                     const icon_el = this.el.querySelector('.toggle-occupants');
                     if (this.model.get('hidden_occupants')) {
-                        this.el.querySelector('.chat-area').classList.add('full');
+                        u.removeClass('fa-angle-double-right', icon_el);
+                        u.addClass('fa-angle-double-left', icon_el);
+                        u.addClass('full', this.el.querySelector('.chat-area'));
                         u.hideElement(this.el.querySelector('.occupants'));
                     } else {
-                        this.el.querySelector('.chat-area').classList.remove('full');
-                        this.el.querySelector('.occupants').classList.remove('hidden');
+                        u.addClass('fa-angle-double-right', icon_el);
+                        u.removeClass('fa-angle-double-left', icon_el);
+                        u.removeClass('full', this.el.querySelector('.chat-area'));
+                        u.removeClass('hidden', this.el.querySelector('.occupants'));
                     }
                     this.occupantsview.setOccupantsHeight();
                 },

src/templates/chatroom_toolbar.html

@@ -8,5 +8,5 @@
 <li class="toggle-call fa fa-phone" title="{{{o.label_start_call}}}"></li>
 {[ } ]}
 {[ if (o.show_occupants_toggle)  { ]}
-<li class="toggle-occupants fa fa-users" title="{{{o.label_hide_occupants}}}"></li>
+<li class="toggle-occupants fa fa-angle-double-right" title="{{{o.label_hide_occupants}}}"></li>
 {[ } ]}