HTML output appears to not render properly

**Describe the bug**
Section headings don't render and instead display the raw Markdown.

**To Reproduce**
1. Navigate to [the homepage](https://tweag.github.io/funflow/)
2. Click "get started"

**Expected behavior**
Section headings should render as designated in the Markdown (i.e., according to the `#` count

**Environment**
Firefox 108, Ubuntu 20
