The play button on embedded assets

Embedded Nira assets show a "play" overlay button, and the Nira session starts when the viewer presses it. This step keeps Nira servers from being overloaded when assets are embedded in a popular publication or when several assets are embedded on the same page.

Multi-page embed example: https://embed-example.nira.app/multi

Skip Asset Preview, which let embedded assets start without the play button, is no longer offered.