Add featured code projects "above the fold" on homepage

Users visiting the site might want to see some of the neat projects that have been open sourced within the DoD. It would be good to have a snapshot of two or three of these on the homepage, above the fold.

(Perhaps a slideshow instead of the static hero element?)

首先检查主页及其当前的静态 hero 元素。确定应如何选择两个或三个开源 DoD 项目并将其呈现在首屏上，然后验证主页是否显示了已确定的精选项目快照，以及所选择的呈现方式是否可用。

由索引模型根据 Issue 内容生成。