Document GraalVM Native support in reference documentation

[bclozel]

Support for AOT and GraalVM Native images has been shipped with #495.

While annotated controllers are supported automatically, there are still cases where developers are required to contribute hints for their applications. For example, registering a DataFetcher "manually" with the wiring configuration will not expose the Java types for reflection at runtime. Also, GraphQlClient usage cannot discover Java types linked to the schema, as there are no beans in the application context and they are not exposed through method signatures.

We need to document these cases with concrete code snippets.