New NUGET format, compatible with "PackageReference" and .NET Core

AspNetSaml.nuspec

@@ -1,8 +1,8 @@
 <?xml version="1.0" encoding="utf-8"?>
-<package xmlns="http://schemas.microsoft.com/packaging/2011/08/nuspec.xsd">
+<package>
   <metadata>
     <id>AspNetSaml</id>
-    <version>1.2.3</version>
+    <version>1.2.4</version>
     <authors>jitbit</authors>
     <owners>jitbit</owners>
     <requireLicenseAcceptance>false</requireLicenseAcceptance>
@@ -13,9 +13,13 @@
     <releaseNotes>Fixes and improvements</releaseNotes>
     <copyright>Copyright Jitbit 2017-2020</copyright>
     <tags>SAML ASP.NET</tags>
+	<contentFiles>
+      <files include="**/Saml.cs" flatten="true" />
+    </contentFiles>
   </metadata>
   <files>
     <!-- Add files from an arbitrary folder that's not necessarily in the project -->
+    <file src="Saml.cs" target="contentFiles\any\any" />
     <file src="Saml.cs" target="content" />
   </files>
 </package>