First of all sorry if this is not the right place to share what I did.
I use webhooks with Emby to turn my lights on/off (I don’t use the Emby integration because it has some problems).
I want it to do the same thing while watching Netflix (I watch Netflix through Chrome/Firefox since I have my PC connected to the TV).
So, what I did was to create a Web Extension that sends webhooks on play/pause Netflix events.
It’s my first Web Extension so there’s is probably things to adjust, but I think it could by useful for someone else.