Add jsonb.close() to all code examples in documentation

Docs show using `jsonb.fromJson()` and `jsonb.toJson()` following `Jsonb jsonb = JsonbBuilder.create()`, but the docs are highly misleading in not showing the required `jsonb.close()` calls.

Update the docs to show the use of `jsonb.close()` or try-with-resources in **all** examples where a `Jsonb` instance is retrieved.

JSON-B implementations can memory-leak if `close()` is never called.

Johnzon is confirmed to leak if a local-scope `Jsonb` instance is never closed in a frequently used method (for example, in a MicroProfile Health implementation).

Search the documentation for every example that retrieves a Jsonb instance with JsonbBuilder.create(), then review how each instance is used. Done means all such examples show jsonb.close() or use try-with-resources, including the fromJson() and toJson() examples.

Written by the indexing model from the issue text.