chore: 隐藏公告关闭窗口，底部添加关闭按钮

src/MaaWpfGui/ViewModels/UI/AnnouncementViewModel.cs

@@ -97,5 +97,10 @@ namespace MaaWpfGui.ViewModels.UI
             ETagCache.Set(response);
             ETagCache.Save();
         }
+
+        public void Close()
+        {
+            RequestClose();
+        }
     }
 }

src/MaaWpfGui/Views/UI/AnnouncementView.xaml

@@ -15,6 +15,7 @@
     Height="500"
     d:DataContext="{d:DesignInstance {x:Type ui:AnnouncementViewModel}}"
     Icon="../../newlogo.ico"
+    ShowCloseButton="False"
     mc:Ignorable="d">
     <ScrollViewer Background="{DynamicResource VersionUpdateViewBackgroundBrush}">
         <StackPanel>
@@ -39,6 +40,12 @@
                 VerticalContentAlignment="Center"
                 Content="{DynamicResource ShowDisclaimerNoMore}"
                 IsChecked="{Binding DoNotRemindThisAnnouncementAgain}" />
+
+            <Button
+                Height="50"
+                MinWidth="100"
+                Command="{s:Action Close}"
+                Content="{DynamicResource Confirm}" />
         </StackPanel>
     </ScrollViewer>
 </hc:Window>