Add PackageReadmeFile node

Author: acoumb

src/Umbraco.Cms.Integrations.SEO.Semrush/Umbraco.Cms.Integrations.SEO.Semrush.csproj

@@ -15,6 +15,7 @@
 		<Company>Umbraco</Company>
 		<PackageTags>Umbraco;Umbraco-Marketplace</PackageTags>
 		<PackageIcon>semrush.png</PackageIcon>
+		<PackageReadmeFile>readme.md</PackageReadmeFile>
 	</PropertyGroup>
 
 	<ItemGroup Condition="'$(TargetFramework)' == 'net472'">