Adapter specification incomplete

From the [specification](https://github.com/eclipse-ee4j/jsonb-api/blob/599481cab6ecccf9eae3b6ab33bef174ec3c11ef/spec/src/main/asciidoc/jsonb.adoc#471-adapters):

> There are two ways how to register JsonbAdapter:
> 1. Using JsonbConfig::withAdapters method;
> 2. Annotating a class field with JsonbTypeAdapter annotation.

However, the [JsonbTypeAdapter annotation](https://javadoc.io/static/javax.json.bind/javax.json.bind-api/1.0/javax/json/bind/annotation/JsonbTypeAdapter.html) has as possible targets `ANNOTATION_TYPE` , `TYPE`, `FIELD`, `METHOD`, which means that you can also annotate a class itself with this annotation and not just a class field.

I'm being a bit pedantic, but I thought I'd create an issue so this can be clarified in future versions of the specification.

Review the adapters section in spec/src/main/asciidoc/jsonb.adoc, especially section 4.7.1, alongside the JsonbTypeAdapter annotation targets linked in the issue. Clarify the specification so it accurately describes all supported registration targets, then verify the surrounding adapter documentation remains consistent.

Written by the indexing model from the issue text.