Need documentation describing how to update the JIT-EE interface #13461

With the addition of crossgen2 to the build, updating the JIT-EE interface is considerably more complex. Before, it required updating the JIT-EE interface GUID, updating the JIT and VM code, and updating SuperPMI. Now, it requires updating crossgen2 as well.

This issue tracks creating a document to describe this, as mentioned here: dotnet/coreclr#26418 (comment)