Added new guide and modified the directory of the documentation site!

In this devlog, I added a new page for the DOS setup and usage guide!

As the pages in my documentation site are getting more and more, I decided to create a folder, and move the guides in, so the navbar would be less cluttered.

One problem I faced though was the CSS and icons not loading in the guide, as the directories were getting a little complicated, given that I am using the /docs directory in my repo for the site, which makes URLs without the full path returning 404. After a few commits (localhost was not using /docs as the root of the site), I finally found the right URL!