Feature Request

• Yes, I reviewed the contribution guidelines.

Describe your use case and the problem you are facing

When a .po file is updated with WP-CLI, the PO-Revision-Date is not updated.

For developers not relying on other tools to manager the language files, it can be easy to forget to update this info.

Describe the solution you'd like

It would be great to update the PO-Revision-Date automatically each time you run the update-po sub-command.