Cargo is missing in the Introduction/Homepage

[mikong]

In the list of chapters, Cargo is between Crates (chapter 11) and Attributes (chapter 13). However, the homepage is missing a link to the Cargo chapter.

I'd like to add a link to the Cargo chapter to the list along with a basic description:

• Cargo - Go through some basic features of the official Rust package management tool.

I'm happy to take suggestions on a better description.

Also, do we need to update #978?

I've noticed several problems with the homepage, but I'd like to keep this issue focused on just the missing Cargo chapter item. I'll open a separate issue to list the other problems. However, one problem related to this missing chapter link is the use of an unordered list. It's easier to notice a missing chapter if we have an ordered list instead. Should we make the switch? I can include a change to an ordered list when I submit a PR for this depending on feedback.