Migration guide for 3.0

Hi

We used Eclipse Soteria in our project and after migration to 3.0 (Jakarta EE 10) our project failed to compile because these public methods where removed:

import static org.glassfish.soteria.mechanisms.jaspic.Jaspic.deregisterServerAuthModule;
import static org.glassfish.soteria.mechanisms.jaspic.Jaspic.registerServerAuthModule;

We couldn't find any hints in the documentation how to handle that so we had to deep dive into the source code and find out about AuthConfigFactory and their usage.
So it would be nice to create a section in README to explain how to deal with these issues during migration.

Update the README with a migration section for version 3.0 and Jakarta EE 10. Start by reviewing the removed Jaspic.registerServerAuthModule and deregisterServerAuthModule methods and the AuthConfigFactory usage mentioned in the issue. Done means the guide clearly explains how users should replace those calls during migration.

Written by the indexing model from the issue text.