Document how to use and configure jqa-rdbms-plugin from maven pom

[StephanPirnbaum]

Transferred from jqassistant-archive#6

I would like to run the RDBMS plugin with the jqassistant maven plugin, however I can't figure who to make it work.
https://stackoverflow.com/questions/62259763/integrate-jqassistant-maven-plugin-with-database-analysis-via-rdbms-plugin suggested this should be supported.

I can't figure if connection properties should be added in section of jqassistant maven plugin configuration, or as plain properties in section, if the section should comport a specific configuration, ...

Thanks in advance!