Add readme to jpa/examples to explain the contents

[odrotbohm]

No description provided.

[dbnex14]

absolutely needed I agree. I am looking to connect multiple databases (e.g. Oracle, DB2) using Spring JPA and I see no settings for that at all for example. Yet all examples outthere use application.properties to set the connection information, hibernate dialect etc.
It would be great if there were better instructions and if missing application.properties files could be provided.

[odrotbohm]

I am not convinced that any specific database configuration instructions suit well in this repository. It is about showcasing high-level features of Spring Data, not low-level infrastructure setup. For a Spring Boot-based setup, this section of the reference documentation might be a good starting point.