Ignore "Content already exists in this project" error

### Please avoid duplicates

- [X] I checked [all open bugs](https://github.com/gr2m/github-project/issues?q=is%3Aissue+is%3Aopen+label%3Abug) and none of them matched my problem.

### Reproducible test case

_No response_

### Please select the environment(s) that are relevant to your bug report

- [ ] Browsers
- [ ] Node
- [ ] Deno

### Versions

latest

### What happened?

I haven't tried to reproduce it, but I got this error in a production app:

```
GraphqlResponseError: Request failed due to following response errors:
- Content already exists in this project
```

I assume it occurs when trying to add an issue or pull requse to a project that was already added, but I thought that theGraphQL API is already handling that gracefully. Maybe there is some racing condition?

### Would you be interested in contributing a fix?

- [ ] yes

Commencez par reproduire le GraphQLResponseError signalé lors de l’ajout d’un issue ou d’une pull request déjà présent dans un projet, en utilisant la dernière version et l’environnement Node ou Deno concerné. Considérez le travail comme terminé lorsque le traitement est géré proprement sans l’erreur « Content already exists in this project » ; le rapport ne fournit ni cas de test ni fichier de départ.

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