RFE: Add keyring CLI options for config_root() and data_root()

The readme documents this well, but for many I suspect a command line option for each would be welcome.

Proposal:
--config_root and --data_root, each just running the documented query and exiting.

If this is acceptable, I'll attempt a pull-request.

Thank you for keyring

Start with the README sections documenting config_root() and data_root(), then locate the keyring CLI entry point that handles commands and options. Add --config_root and --data_root so each prints its documented query result and exits; verify both options work as described.

Written by the indexing model from the issue text.