How do I get headings in a .md file to appear in the TOC?

**Operating System**: (`Windows`)

**DocFX Version Used**:

**Template used**: (`default`)

**Steps to Reproduce**:

1. Go to [Tutorial](https://dotnet.github.io/docfx/tutorial/docfx_getting_started.html). All of the headings from the .md files are included in the TOC.
2. Go to [Tutorial TOC.yml](https://github.com/dotnet/docfx/blob/dev/Documentation/tutorial/toc.yml). The toc.yml file includes the tutorial's .md files.
How are the headings from the .md files appearing in the published TOC? They don't appear for me.

**Expected Behavior**:
All of the # headings in my .md files should appear in the published TOC.
**Actual Behavior**:
Only the "name: Topic Name" entries appear in my published TOC.