extensions-app: Port config to ESM

The app uses a different Config module than the rest of the code
base, so we can port it separately.

Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/2868>

subprojects/extensions-app/js/main.js

@@ -10,7 +10,7 @@ const Package = imports.package;
 
 Package.initFormat();
 
-const Config = imports.misc.config;
+import * as Config from './misc/config.js';
 import * as ExtensionUtils from './misc/extensionUtils.js';
 
 import {ExtensionState, ExtensionType}  from './misc/extensionUtils.js';

subprojects/extensions-app/js/misc/config.js.in

@@ -1 +1 @@
-var PROFILE = '@PROFILE@';
+export const PROFILE = '@PROFILE@';