Clarify details in PipelineExecutionStepState

The `details` element in https://github.com/AdobeDocs/cloudmanager-api-docs/blob/b6c0678a414f112dba41e3bc8ecbf324385cd20f/swagger-specs/api.yaml#L1707 does not define which map keys to expect there.

I have seen the following details map

```
"environmentUrls": [
{
"instanceType": "author",
"instanceUrl": "https://author-p7802-e44859.adobeaemcloud.com"
},
{
"instanceType": "publish",
"instanceUrl": "https://publish-p7802-e44859.adobeaemcloud.com"
}
],
"deploymentStepDescription": "[{\"id\":1,\"stepAction\":\"update-author-indexes\",\"updated\":\"2020-11-02T13:24:11.870+0000\"},{\"id\":2,\"stepAction\":\"update-publish-indexes\",\"updated\":\"2020-11-02T13:27:22.581+0000\"},{\"id\":3,\"stepAction\":\"update-services\",\"updated\":\"2020-11-02T13:27:46.629+0000\"},{\"id\":4,\"stepAction\":\"install-mutable-content\",\"updated\":\"2020-11-02T13:37:18.741+0000\"}]"
```

Would be nice to clarify this in a model or at least in some accompanying markdown document.

Examinez swagger-specs/api.yaml à la ligne 1707 et inspectez la définition des détails de PipelineExecutionStepState. Documentez les clés observées environmentUrls et deploymentStepDescription dans le modèle ou dans un document Markdown associé, en rendant claire la structure attendue pour les utilisateurs de l’API.

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