Cross reference links can lead to 404 pages

The latest version of the program supports cross-references like `[ClassName.method]`, etc. but the links don't always work. Part of the problem cannot be fixed without input from the user.

## The problem

When previewing markdown documents on your desktop, the links should point to markdown files to work, as you're browsing through your file system. E.g. `ClassName.md`

If you convert to html and/or put the files on the web, the links should point to the page's name or file, `./ClassName` or `./ClassName.html` or the lowercase equivalents.

Hugo may change the case of the links depending on the website's settings I believe?

## Solution

For markdown, I'm currently linking to `../PageName`. This *should* work if you put your pages online with a CMS, but it won't if you output your files as html directly. To solve this, we might need to have an html output that writes links as `../pagename.html#header-name`. We can look at how Sphinx and the Godot docs handle that.

In the hugo format, links should probably use the `{{< relref >}}` shortcode. This shortcode takes a relative path to a markdown document and resolves the final path for you. We have the exact name of the markdown documents so this would work reliably.