Bump AngleSharp from 1.4.0 to 1.5.1

---
updated-dependencies:
- dependency-name: AngleSharp
  dependency-version: 1.5.1
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

src/Html2Markdown/Html2Markdown.csproj

@@ -15,7 +15,7 @@
     </PropertyGroup>
 
     <ItemGroup>
-        <PackageReference Include="AngleSharp" Version="1.4.0"/>
+        <PackageReference Include="AngleSharp" Version="1.5.1"/>
     </ItemGroup>
 
     <ItemGroup>