Warn before software closed; fix bug on first run

Also put settings into proper dir

src/Interfaces/ICanCheckShutdown.cs

@@ -0,0 +1,8 @@
+using System.Threading.Tasks;
+
+namespace MayShow.Interfaces;
+
+interface ICanCheckShutdown
+{
+    Task<bool> CheckIsSafeToShutdown();
+}

src/Interfaces/IChangeViewModel.cs

@@ -1,10 +1,9 @@
 using MayShow.ViewModels;
 
-namespace MayShow.Interfaces
+namespace MayShow.Interfaces;
+
+interface IChangeViewModel
 {
-    interface IChangeViewModel
-    {
-        void PushViewModel(BaseViewModel model);
-        void PopViewModel();
-    }
+    void PushViewModel(BaseViewModel model);
+    void PopViewModel();
 }

src/Interfaces/ITopLevelGrabber.cs

@@ -1,9 +1,8 @@
 using Avalonia.Controls;
 
-namespace MayShow.Interfaces
+namespace MayShow.Interfaces;
+
+interface ITopLevelGrabber
 {
-    interface ITopLevelGrabber
-    {
-        TopLevel GetTopLevel();
-    }
+    TopLevel GetTopLevel();
 }