Bump CommunityToolkit.Mvvm from 8.0.0 to 8.4.0

---
updated-dependencies:
- dependency-name: CommunityToolkit.Mvvm
  dependency-version: 8.4.0
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

SharpGallery.csproj

@@ -28,7 +28,7 @@
       <IncludeAssets Condition="'$(Configuration)' != 'Debug'">None</IncludeAssets>
       <PrivateAssets Condition="'$(Configuration)' != 'Debug'">All</PrivateAssets>
     </PackageReference>
-    <PackageReference Include="CommunityToolkit.Mvvm" Version="8.0.0" />
+    <PackageReference Include="CommunityToolkit.Mvvm" Version="8.4.0" />
 
     <!-- Auto Updates -->
     <PackageReference Include="Velopack" Version="0.0.61" />