`gh stack submit` does not respect org-wide PR template

My organisation has an org-wide PR template, just as the one described here: https://github.com/orgs/community/discussions/183776. We used to have these templates in each repo, but they were all the same and repetitve, so we decided to define them in one place. We'd rather not go back to per-repo template.

Unfortunately, `gh stack submit` does not seem to respect them. User has two options with this command:
* By default it opens CLI dialog to enter PR's title and description. It doesn't use the org template
* `--auto` creates PR with some pre-populated footer and nothing else. Again no template is used.

The command supports repo-wide templates, thanks to https://github.com/github/gh-stack/pull/77, but this PR does not seem to take org-wide templates into account.

Commencez par suivre le point d’entrée `gh stack submit` ainsi que ses chemins du dialogue par défaut et de `--auto`, en utilisant github/gh-stack pull request #77 comme contexte pour les templates à l’échelle du dépôt. Reproduisez les deux modes avec un template de PR à l’échelle de l’organisation, puis vérifiez que la pull request résultante inclut ce template sans perdre le footer existant.

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