Bump MarkdownSnippets.MsBuild from 28.0.0-beta.11 to 28.0.0-beta.18

---
updated-dependencies:
- dependency-name: MarkdownSnippets.MsBuild
  dependency-version: 28.0.0-beta.18
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

src/Directory.Packages.props

@@ -10,7 +10,7 @@
     <PackageVersion Include="Aspose.Slides.NET" Version="25.10.0" />
     <PackageVersion Include="Aspose.Words" Version="25.10.0" />
     <PackageVersion Include="DeterministicIoPackaging" Version="0.15.0" />
-    <PackageVersion Include="MarkdownSnippets.MsBuild" Version="28.0.0-beta.11" />
+    <PackageVersion Include="MarkdownSnippets.MsBuild" Version="28.0.0-beta.18" />
     <PackageVersion Include="Microsoft.NET.Test.Sdk" Version="18.0.1" />
     <PackageVersion Include="NUnit" Version="4.4.0" />
     <PackageVersion Include="NUnit3TestAdapter" Version="6.1.0" />