feat: support for `[[wikilinks]]` as an optional initializer

[jaredcwhite]

In order to enable support for wiki-like content sources (aka an Obsidian content vault), we should support the wikilinks syntax. I've already written a plugin for a wiki-type site, so copying that over as a first-party solution won't be difficult. I worked on a solution with simple regex, but I think it'll fall apart on certain types of content where that syntax should be ignored in the text so might need some more detailed thinking.

I'm would imagine we can implement this by supporting adding:

init :wikilinks

to the config/initializers.rb file and boom. This would be useful in conjunction with #515, #884, etc.