Update MimeTypeCore.csproj

Author: lofcz

MimeTypeCore/MimeTypeCore/MimeTypeCore.csproj

@@ -30,4 +30,7 @@
             <_Parameter1>MimeTypeCore.Inserter</_Parameter1>
         </AssemblyAttribute>
     </ItemGroup>
+    <ItemGroup Condition="'$(TargetFramework)' == 'net40'">
+        <PackageReference Include="Microsoft.Bcl.Async" Version="1.0.168" />
+    </ItemGroup>
 </Project>