add volume and brightness control

shell.qml

@@ -1,5 +1,6 @@
 import Quickshell
 import Quickshell.Io
+import qs.config
 import qs.modules
 import qs.services
 
@@ -84,6 +85,52 @@ ShellRoot {
         }
     }
 
+    IpcHandler {
+        target: "controls"
+
+        function toggle(): void {
+            Session.toggle("controls", "");
+        }
+
+        function open(): void {
+            Session.open("controls", "");
+        }
+
+        function close(): void {
+            Session.close();
+        }
+    }
+
+    // Not a menu: these are for the volume and brightness keys, which want to
+    // move the level without putting anything on screen.
+    IpcHandler {
+        target: "volume"
+
+        function up(): void {
+            Audio.step(Config.volumeStep);
+        }
+
+        function down(): void {
+            Audio.step(-Config.volumeStep);
+        }
+
+        function mute(): void {
+            Audio.toggleMute();
+        }
+    }
+
+    IpcHandler {
+        target: "brightness"
+
+        function up(): void {
+            Brightness.step(Config.brightnessStep);
+        }
+
+        function down(): void {
+            Brightness.step(-Config.brightnessStep);
+        }
+    }
+
     IpcHandler {
         target: "bluetooth"