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 but it is rather out of date and does not have the required links either.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.*}

从 parquet.apache.org/downloads/ 上的项目下载页面开始，并将其与 issue 中引用的 Apache 发布分发下载链接要求进行比较。更新页面，使其包含所需的 KEYS、签名、哈希值和开源发布版本链接，然后确认该页面是最新的并符合这些要求。

由索引模型根据 Issue 内容生成。