Used in conjunction with newAndUpdated plugin.
Display new listings that were added in the previous 'x' days. The value can be quite flexible. For instance, these all work:
[rover_idx_plugin plugin_type="newAndUpdated" date_added="1 month"]
[rover_idx_plugin plugin_type="newAndUpdated" date_added="4 days"]
[rover_idx_plugin plugin_type="newAndUpdated" date_added="2 weeks"]
Default is to ignore this parameter, in favor of prev_days="7 days".