The question at "Why is one not allowed to use a Boolean in a docker-compose.yml?" is about docker-compose but there is not such a tag.
You can do it yourself—simply type docker-compose into the tag entry box, and it will be created.
In private beta, creating tags only requires 1 reputation point. When we leave private beta and the privilege levels increase, it should be sufficient to leave a little notice at the end of the post asking for the tag to be added (or perhaps leave a comment).
In public beta, 150 reputation will be required, and after graduation, 300 rep is required (see Reputation requirements compared on Meta.SE).