Document data tables

[mike-solomon]

A community member recently added support for printing out data tables in the rewrite-maven-plugin. We should add docs that explain how to use this - similar to what we've done in the Moderne docs

As of May 1st, this is only available in the snapshot for the Maven plugin. You can run a command to print a data table as a CSV to the target/ directory in a timestamped folder.

We should make it clear that this is primarily for testing and isn't that helpful when run on a single repository. The main benefit comes from running it at scale through Moderne.