Add advertisments for third party dependencies before/after download

To get the best user experience from Cryptomator, users should install und setup third party applications.
If we display advertisement for those applications directly before/during/after the download of the setup program, we would have less user using old legacy components.

首先检查 Cryptomator Website 的安装程序下载流程。Issue 未指明任何文件或测试，因此首先明确应宣传哪些第三方应用，以及展示位置应在下载之前、期间还是之后；完成标准应是一个已定义且获批准的广告体验。

由索引模型根据 Issue 内容生成。