Project download page does not conform to Apache requirements

Our last two release announcements were rejected on the following grounds:
> Sorry, but the download page does not contain the required links to KEYS, sigs and hashes.
>
> Please see:
>
>
> and the previous section
>
> There is a project download page at:
>
>
> but it is rather out of date and does not have the required links either.
> Note that the ASF releases open source, so the download page must include that.

**Reporter**: [Zoltan Ivanfi](https://issues.apache.org/jira/secure/ViewProfile.jspa?name=zi) / @zivanfi

_{**Note**: *This issue was originally created as [PARQUET-1298](https://issues.apache.org/jira/browse/PARQUET-1298). Please see the [migration documentation](https://issues.apache.org/jira/browse/PARQUET-2502) for further details.*}

Commencez par la page de téléchargement du projet à l’adresse parquet.apache.org/downloads/ et comparez-la aux exigences d’Apache concernant les liens de téléchargement des distributions de release citées dans l’issue. Mettez à jour la page pour inclure les liens requis vers KEYS, la signature, le hash et les releases open source, puis vérifiez que la page est à jour et conforme à ces exigences.

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