Added UI support for LINUX KDE Plasma

PluginManager/UX/IOutputModel.cs

@@ -0,0 +1,29 @@
+using System.Threading.Tasks;
+
+namespace PluginManager.UX;
+
+public enum MessageBoxType
+{
+    Info,
+    Warning,
+    Error
+}
+
+public enum MessageBoxButtons
+{
+    YesNo,
+    YesNoCancel,
+    ContinueCancel,
+}
+
+internal interface IOutputModel
+{
+    
+    internal Task ShowMessageBox(string title, string message, MessageBoxType type);
+    internal Task<string> ShowInputBox(string title, string message);
+
+    internal Task ShowMessageBox(string message);
+    internal Task<int> ShowMessageBox(string title, string message, MessageBoxButtons buttons, bool isWarning);
+    
+    internal Task ShowNotification(string title, string message, int timeout_seconds = 5);
+}