plugins/desktop-widgets: create a new "desktop" widget plugin type

- Draggable per-monitor background layer widgets
- Add basic dms version checks on plugins
- Clock: built-in clock desktop plugin
- dgop: built-in system monitor desktop plugin

quickshell/Modules/Plugins/DesktopPluginComponent.qml

@@ -0,0 +1,49 @@
+import QtQuick
+import qs.Common
+
+Item {
+    id: root
+
+    property var pluginService: null
+    property string pluginId: ""
+
+    property real widgetWidth: 200
+    property real widgetHeight: 200
+    property real minWidth: 100
+    property real minHeight: 100
+
+    property var pluginData: ({})
+
+    Component.onCompleted: loadPluginData()
+    onPluginServiceChanged: loadPluginData()
+    onPluginIdChanged: loadPluginData()
+
+    Connections {
+        target: pluginService
+        function onPluginDataChanged(changedPluginId) {
+            if (changedPluginId !== pluginId)
+                return;
+            loadPluginData();
+        }
+    }
+
+    function loadPluginData() {
+        if (!pluginService || !pluginId) {
+            pluginData = {};
+            return;
+        }
+        pluginData = SettingsData.getPluginSettingsForPlugin(pluginId);
+    }
+
+    function getData(key, defaultValue) {
+        if (!pluginService || !pluginId)
+            return defaultValue;
+        return pluginService.loadPluginData(pluginId, key, defaultValue);
+    }
+
+    function setData(key, value) {
+        if (!pluginService || !pluginId)
+            return;
+        pluginService.savePluginData(pluginId, key, value);
+    }
+}