toggle_sidebar: switch icon on click

plugins/toggle_sidebar/init.js

@@ -0,0 +1,9 @@
+Plugins.Toggle_Sidebar = {
+    toggle: function() {
+        Feeds.toggle();
+
+        const label = document.querySelector("i.toggle-sidebar-label");
+
+        label.innerHTML = Element.visible("feeds-holder") ? 'chevron_left' : 'chevron_right';
+    }
+};