Convert to use ESM modules

See: https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/1499

js/ui/realms/realmIndicator.js

@@ -1,7 +1,11 @@
-const { Clutter, GObject, Shell, St } = imports.gi;
-const PanelMenu = imports.ui.panelMenu;
+import Clutter from 'gi://Clutter';
+import GObject from 'gi://GObject';
+import Shell from 'gi://Shell';
+import St from 'gi://St';
 
-var RealmPanelIndicator = GObject.registerClass(
+import * as PanelMenu from '../panelMenu.js';
+
+export const RealmPanelIndicator = GObject.registerClass(
 class RealmPanelIndicator extends PanelMenu.Button {
         _init() {
             super._init(0.5, "Current Realm");