docs(migration): add entry for 2.2.1.Final
Notes for upgrading to newer versions of Apiman.
Unless stated otherwise, the instructions assume that you are upgrading sequentially version to version.
+== Migrating to 2.2.1.Final
+
+No special action should be required, although backing up is always recommended.
+
== Migrating to 2.2.0.Final
=== WildFly & Keycloak
