extensions-app: Style development window

Libadwaita includes a standard style class to distinguish
nightly/development versions from regular instances, but
we never to around applying it.

Do that now.

Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/2841>

subprojects/extensions-app/js/main.js

@@ -10,6 +10,7 @@ const Package = imports.package;
 
 Package.initFormat();
 
+const Config = imports.misc.config;
 const ExtensionUtils = imports.misc.extensionUtils;
 
 const { ExtensionState, ExtensionType } = ExtensionUtils;
@@ -94,6 +95,9 @@ var ExtensionsWindow = GObject.registerClass({
     _init(params) {
         super._init(params);
 
+        if (Config.PROFILE === 'development')
+            this.add_css_class('devel');
+
         this._updatesCheckId = 0;
 
         this._exporter = new Shew.WindowExporter({ window: this });

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

@@ -1 +1,2 @@
 var PACKAGE_VERSION = '@PACKAGE_VERSION@';
+var PROFILE = '@PROFILE@';

subprojects/extensions-app/js/misc/meson.build

@@ -3,5 +3,6 @@ config_js = configure_file(
   output: '@BASENAME@',
   configuration: {
     'GETTEXT_VERSION': meson.project_version(),
+    'PROFILE': get_option('profile'),
   }
 )