examples/java: add required build information

[rjeczalik]

Add build information to https://github.com/scylladb/serverless-examples/tree/main/jhelloserverless, so the example builds out of the box.

All please add short instruction to the readme how to run the example, the same that was done for Go example:

https://github.com/scylladb/serverless-examples#gohelloserverless

[averemee-si]

Hi Rafal,

Is there any estimation about build documentation availability? Especially for drivers v4?

Thanks!

Regards, Aleksei

[rjeczalik]

Hey @averemee-si! Please stay tuned, we are going to update all the serverless examples altogether with required build information for out-of-the-box experience. It drags a bit currently unfortunately, as we focus our efforts on the upcoming Scylla Summit.