Add an {{advert}} variable to the Now Playing placeholders
The Now Playing option has a selection of variables to describe the content on air: https://docs.playitsoftware.com/PlayItLive/216/now_playing_placeholders.html
A useful one to add would be {{advert}}, which would be `true` when an Advert Block is playing and `false` otherwise. This would allow the "commercial" field to be sent to the TuneIn AIR API: https://cms.tunein.com/broadcasters/api/