Create mention helper

[tmpfs]

To reference a person in the config authors list by identifier.

Needs to support:

• Name only
• Name and anchor hyperlink
• Name and hyperlink with avatar

[tmpfs]

Suggested partial names for std::author:

• [x] attribution: List authors by name comma-delimited.
• [x] mention: Show a @nickname handle with link
• [x] cite: Link to an author by name.
• [ ] avatar: Link to the website for an author using an avatar image.

[tmpfs]

Consider supporting @ style syntax in the wiki links format, so we could do something like this:

[[@tmpfs]]

To link to an author.