envbuilder don't recognize "dockerComposeFile" param

Hi! My devcontainer.json looks like this:

```json
{
"name": "keycrm",
"dockerComposeFile": [
"../example.docker-compose.yml"
],
"service": "app",
"services": ["app", "db"],
"forwardPorts": [80],
"postAttachCommand": "service apache2 start",
"extensions": [
"felixfbecker.php-pack",
"cweijan.vscode-mysql-client2"
]
}
```

and coder don't recognize "dockerComposeFile" option. It's described in devcontainer.json schema, and supported by my IDE (phpstorm) as well. But when I'm trying to create a workspace with such devcontainer it usually fallback to default image.
So, maybee in future, would envbuilder support docker-compose files to build, or I'm using it in wrong way? I'm trying to make developer's workspace with standalone environment, but creating only "app" is not enough in case of no DB.

Commencez par le devcontainer.json fourni et ../example.docker-compose.yml, puis retracez la manière dont envbuilder gère l’option dockerComposeFile par rapport à son chemin d’image par défaut. Déterminez si les services app et db doivent être construits et démarrés, et vérifiez qu’un workspace utilisant cette configuration ne revient plus à l’image par défaut.

Rédigé par le modèle d'indexation à partir du texte de l'issue.