[Bug] Custom template doesn't load

**Describe the bug**
Just tried this simple step.
https://dotnet.github.io/docfx/docs/template.html?tabs=modern#custom-template

**To Reproduce**
Under the docs folder, I have created a folder called aecom-template.
Added to the docfx.json file

```
"template": [
"default",
"modern",
"aecom-template"
],
```
Used the main.css and main.js as documentation, but nothing happened.
I don't have the GitHub logo, and no colour is changed.

**Expected behavior**
I am expected to see the GitHub logo and the same green colour you have on your website, adding those steps.

**Context (please complete the following information):**
- OS: Windows
- Docfx version: 2.77