Replace old markdown and remove redundant events (#389)

* Remove redundant messages

* Replaced old markdown with preview.
Added nuget config to add preview feed

* Fix old extensions usage

* Scrollbar margin for the markdown.

---------

Co-authored-by: Burak Kaan Köse <bkaankose@outlook.com>

Wino.Core.UWP/Services/StatePersistenceService.cs

@@ -40,7 +40,6 @@ namespace Wino.Services
                 if (SetProperty(ref isReadingMail, value))
                 {
                     OnPropertyChanged(nameof(IsBackButtonVisible));
-                    WeakReferenceMessenger.Default.Send(new ShellStateUpdated());
                 }
             }
         }
@@ -63,7 +62,6 @@ namespace Wino.Services
                 if (SetProperty(ref isReaderNarrowed, value))
                 {
                     OnPropertyChanged(nameof(IsBackButtonVisible));
-                    WeakReferenceMessenger.Default.Send(new ShellStateUpdated());
                 }
             }
         }