Show notification on first run after an update with a link to the changelog

Closes #487

DiscordChatExporter.Gui/App.xaml.cs

@@ -15,9 +15,11 @@ public partial class App
 
     public static string VersionString { get; } = Version.ToString(3);
 
-    public static string GitHubProjectUrl { get; } = "https://github.com/Tyrrrz/DiscordChatExporter";
+    public static string ProjectUrl { get; } = "https://github.com/Tyrrrz/DiscordChatExporter";
 
-    public static string GitHubProjectDocsUrl { get; } = GitHubProjectUrl + "/blob/master/.docs";
+    public static string ChangelogUrl { get; } = ProjectUrl + "/blob/master/Changelog.md";
+
+    public static string DocumentationUrl { get; } = ProjectUrl + "/blob/master/.docs";
 }
 
 public partial class App

DiscordChatExporter.Gui/Services/SettingsService.cs

@@ -1,4 +1,5 @@
-using DiscordChatExporter.Core.Exporting;
+using System;
+using DiscordChatExporter.Core.Exporting;
 using Microsoft.Win32;
 using Tyrrrz.Settings;
 
@@ -20,6 +21,8 @@ public partial class SettingsService : SettingsManager
 
     public bool ShouldReuseAssets { get; set; }
 
+    public Version? LastAppVersion { get; set; }
+
     public string? LastToken { get; set; }
 
     public ExportFormat LastExportFormat { get; set; } = ExportFormat.HtmlDark;

DiscordChatExporter.Gui/ViewModels/Components/DashboardViewModel.cs

@@ -83,7 +83,7 @@ public class DashboardViewModel : PropertyChangedBase
         await _dialogManager.ShowDialogAsync(dialog);
     }
 
-    public void ShowHelp() => ProcessEx.StartShellExecute(App.GitHubProjectDocsUrl);
+    public void ShowHelp() => ProcessEx.StartShellExecute(App.DocumentationUrl);
 
     public bool CanPopulateGuildsAndChannels =>
         !IsBusy && !string.IsNullOrWhiteSpace(Token);

DiscordChatExporter.Gui/ViewModels/RootViewModel.cs

@@ -106,6 +106,7 @@ public class RootViewModel : Screen, IHandle<NotificationMessage>, IDisposable
 
         _settingsService.Load();
 
+        // Sync theme with settings
         if (_settingsService.IsDarkModeEnabled)
         {
             App.SetDarkTheme();
@@ -114,6 +115,18 @@ public class RootViewModel : Screen, IHandle<NotificationMessage>, IDisposable
         {
             App.SetLightTheme();
         }
+
+        // App has just been updated, display changelog
+        if (_settingsService.LastAppVersion != App.Version)
+        {
+            Notifications.Enqueue(
+                $"Successfully updated to {App.Name} v{App.VersionString}",
+                "CHANGELOG", () => ProcessEx.StartShellExecute(App.ChangelogUrl)
+            );
+
+            _settingsService.LastAppVersion = App.Version;
+            _settingsService.Save();
+        }
     }
 
     protected override void OnClose()