Allow link completion for multiple file types about wiki.vim

[lervag]

Fascinating. This is a use case I never thought of.

In my view, a yaml file should represent data, somehow - not text. And so, it should be a file: url, not a wiki url. That is, I would have expected a link like <file:yaml1.yaml> or [my yaml file](file:yaml1.yaml) in this particular case.

I do notice that e.g. GitHub will consider [foo](bar.yaml) as a link to the file bar.yaml in the same directory as the current file. I assume this is "general", i.e. [foo](file) will open file regardless of the extension.

For wiki.vim, it still makes sense to differ between the schemes here, as it makes it easier to handle things. But OK, given the g:wiki_filetypes setting, the links already work as expected already. And I think I can see how you would want completion to work similarly.

[lervag]

Ok, I believe this is fixed now.