ToC logic adds headings from snippets in the last position

[theletterf]

Describe the bug

If a snippet contains headings, those are added the last in the ToC.

Expected behavior

I would expect the headings to appear in the ToC according to the order by which all headings are rendered on page.

Steps to reproduce

1. Create a snippet with one or more headings.
2. Include the snippet in a doc.
3. See the ToC's order.

Tooling

• docs-builder
• migration tooling
• I'm not sure