Support Array-style post author

[nykma]

trafficstars

A very stupid implementation. Need further inspect.

My Hugo-style Markdown generator ( ox-hugo ) exports author front-matter as array by default

This patch will let this site be built successfully, but generated data may not meet SEO need.

[victor-pogor]

Hi @nykma.

Thank you for your contribution.

The PR is not ready and I cannot merge it. I'll investigate this implementation but with low priority.