CORS 404 OPTIONS

### Environment
- `lite-server` version: 2.6.1
- `nodejs` version: 10.24.1
- `npm` version: 6.14.12
- OS type/version: MacOS
- bs-config.json:
```
{
"cors": true,
"injectChanges": true,
"logLevel": "debug",
"open": false
}
```

When trying to proxy an html file, I am getting this error in the browser:
> Access to fetch at 'https://d1c50u1zbkqmph.cloudfront.net/monitoring/security/template.html' from origin 'https://app-blah.somedomain.com' has been blocked by CORS policy: Response to preflight request doesn't pass access control check: It does not have HTTP ok status.

Then in the lite-server side, it logged:
> 21.08.04 12:58:06 404 OPTIONS /monitoring/security/template.html

What do I need to do to get this to work? It works for other files such as **json** but not with **html**? **json** files used to failed too, but after I turned on `cors: true` then it worked for **json** but doesn't seems to be the case for **html**.