Bump SixLabors.ImageSharp from 2.1.0 to 3.1.3 in /Shockky.Sandbox (#7)

Bumps [SixLabors.ImageSharp](https://github.com/SixLabors/ImageSharp) from 2.1.0 to 3.1.3.
- [Release notes](https://github.com/SixLabors/ImageSharp/releases)
- [Commits](SixLabors/ImageSharp@v2.1.0...v3.1.3)

---
updated-dependencies:
- dependency-name: SixLabors.ImageSharp
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Shockky.Sandbox/Shockky.Sandbox.csproj

@@ -10,7 +10,7 @@
 	</ItemGroup>
 
 	<ItemGroup>
-		<PackageReference Include="SixLabors.ImageSharp" Version="2.1.0" />
+		<PackageReference Include="SixLabors.ImageSharp" Version="3.1.3" />
 		<PackageReference Include="System.CommandLine" Version="2.0.0-*" />
 	</ItemGroup>