In rustdoc sidebars, most headings are clickable links. For instance, "Required Methods" and "Implementors" in the sidebar of https://doc.rust-lang.org/nightly/std/string/trait.ToString.html.

However, the headings under "Other items in..." are not clickable. We should link those to the appropriate subheading on the module page. That allows the user to see a more verbose listing of items in the module, since each one has a description alongside it.