[BUG] headers aren't displayed, can't be jumped to via ToC

[pcarrin2]

General Information
Version: 0.8.2
Installation Method: home-manager
Operating System: NixOS

Used configuration (if available):
Default configuration

Describe the bug
Headers in articles are not displayed, and I can't jump to a section using the Table of Contents pane on the right-hand side. I can jump to the top of an article, but none of the other sections work.

To Reproduce
Steps to reproduce the behavior:

1. Run wiki-tui linux.
2. Select the first result, titled "Linux." (But any article will do.)
3. Hit Tab to navigate to the Table of Contents pane.
4. Hit J a few times to select a section, for example section 3 (Design), then hit Enter.
5. Nothing happens -- the article is not scrolled to the correct section.
6. Manually scroll down a ways, and notice that section headers are not displayed.
7. From the Table of Contents pane, select the section called "(Top)" and hit Enter.
8. The article is correctly scrolled to the top.

Expected behavior
I expect section headings to show up as text in the article -- perhaps bolded for emphasis.
During step 5, I expect the article to scroll to the correct section after hitting Enter in the ToC pane.

Checklist

• checked other issues for the same bug
• read CONTRIBUTING.md

Note: I ran wiki-tui at log level 0, then checked ~/.cache/wiki-tui.log for info, but there were no messages aside from "successfully initialized the logging system."