Oranda's additional_pages generates HTML files with `.md` suffix, causing all pages to 404

Building the project with any version greater than 0.4.1 in https://github.com/untitaker/spacemod/tree/5e5bd7ceff39a57a1c9e11ef93eec65d47620756 will generate the following nav:

```
<a href="/spacemod/docs/matching/">Matching modes</a>
```

but oranda generated a file `/docs/matching.md`

The last version that works for me is 0.4.1.