Some top-nav entires aren't shown as active when visisted

To see the expected behaviour:

- Visit https://www.docsy.dev
- Click on any top-nav entry, like **About** or **Documentation**
- Notice that when viewing a pager under, say, the **Documentation** section, the corresponding top-nav entry is shown in bold. This is because it has the `active` class applied to it.

Now visit etcd.io. You'll notice that the following top-nav entries are _not_ shown as active (bold) when visited:

- **Docs**
- **Install**

/cc @nate-double-u @kapunahelewong