Add support for markdown wikilinks (aka piped links)

[Mexator]

This PR adds support for Obsidian-style links.

Syntax is [[Link|Display text]]. The rendering to HTML is done with markdown-it-wikilinks

[imysl0]

Use this to prevent generating unnecessary HTML suffixes for MD files.

    mkdown.use(mdWikilinks({
      uriSuffix: ''
    }))

[Mexator]

Use this to prevent generating unnecessary HTML suffixes for MD files.

    mkdown.use(mdWikilinks({
      uriSuffix: ''
    }))

thanks for the suggestion, done

[imysl0]

I tried it, and it works great. I've integrated it into my own instance. Thank you so much!