ags: implement per-monitor brightness control

.config/ags/modules/.configuration/user_options.js

@@ -38,6 +38,9 @@ let configOptions = {
         'warnTitles': ["Low battery", "Very low battery", 'Critical Battery'],
         'warnMessages': ["Plug in the charger", "You there?", 'PLUG THE CHARGER ALREADY'],
     },
+    'brightness': {
+        'controller': "brightnessctl",
+    },
     'music': {
         'preferredPlayer': "plasma-browser-integration",
     },
@@ -159,4 +162,4 @@ function overrideConfigRecursive(userOverrides, configOptions = {}) {
 overrideConfigRecursive(userOverrides, configOptions);
 
 globalThis['userOptions'] = configOptions;
-export default configOptions;
+export default configOptions;