Rearrange files to shared project

src/MayShow.Shared/Interfaces/ICanCheckShutdown.cs

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

src/MayShow.Shared/Interfaces/IChangeViewModel.cs

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+using MayShow.ViewModels;
+
+namespace MayShow.Interfaces;
+
+interface IChangeViewModel
+{
+    void PushViewModel(BaseViewModel model);
+    void PopViewModel();
+}

src/MayShow.Shared/Interfaces/ITopLevelGrabber.cs

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+using Avalonia.Controls;
+
+namespace MayShow.Interfaces;
+
+interface ITopLevelGrabber
+{
+    TopLevel GetTopLevel();
+}