Mention capitalisation differences lead to multiple conflicting HTML outputs

[marcuswhybrow]

[[Mention]] and [[mention]] are a build panic when both exist. The desired capitalisation cannot be reliably determined. The capitalisation effects the display title of the mention, but the mention slug's are the same. i.e. capital "Mention" has slug "mention" but lowercase title "mention" also has slug "mention" (slugs are always kebab-case).

It's a bug because it's no desired behaviour, but a byproduct of the rules.

What to do? Well currently we panic. The panic message helps, but cannot know this was the specific cause because it's only a dumb check looking for file overrites of files already created.

This problem intertwines with #56 and URL redirection, because both problems are collision resolution of build files across time.

Solution? I think there needs to be a check in the markdown mention parser. If a mention exists with the same slug but a different title, throw a specific panic. This sucks beause, a la #62, panic's silently break the devserver until one realises and checks the terminal.