Consume .NET nightly builds

Consume nightly builds of .NET 10.

Author: martincostello

NuGet.config

@@ -3,12 +3,16 @@
   <packageSources>
     <clear />
     <add key="aspnet-contrib" value="https://www.myget.org/F/aspnet-contrib/api/v3/index.json" />
+    <add key="dotnet10" value="https://pkgs.dev.azure.com/dnceng/public/_packaging/dotnet10/nuget/v3/index.json" />
     <add key="NuGet" value="https://api.nuget.org/v3/index.json" />
   </packageSources>
   <packageSourceMapping>
     <packageSource key="aspnet-contrib">
       <package pattern="AspNet.Security.OAuth.GitHub" />
     </packageSource>
+    <packageSource key="dotnet10">
+      <package pattern="*" />
+    </packageSource>
     <packageSource key="NuGet">
       <package pattern="*" />
     </packageSource>