Use Include instead of Update for README.md to fix pack issue

Author: rameel

src/Ramstack.FileSystem.Azure/Ramstack.FileSystem.Azure.csproj

@@ -66,7 +66,7 @@
   </ItemGroup>
 
   <ItemGroup>
-    <None Update="README.md">
+    <None Include="README.md">
       <Link>Properties\README.md</Link>
       <Pack>True</Pack>
       <PackagePath>\</PackagePath>