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

[untitaker]

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.