Could you please help me to prefix attachment permalinks with a custom string (for example attachment)

Such that example/attachment-slug becomes example/attachment/slug?

• Apply only to posts with post_type attachment
• Using PHP that can be added to a custom plugin / mu-plugin / functions.php
• Don’t worry about existing attachments – the code should alter the permalinks of new attachments

Thank you.

Kind regards, Mat

P.S. Related question here