Use git contributors from git log to populate feed items authors

[Guts]

From #34

Thanks for your inputs.

We can add the feature through page.meta.author.

I think we should take into an account that a page can have multiple authors, like co-contributors in git.

git contributor is also a good feature but page.meta.author should override git contributor.

The plugin was first thought to use git information. Nevertheless, we can move forward more easily with the metadata of the page. Let's start by this side, then I'll see the git logic from @timvink plugins.

The formatting should be like this

 <author>
 <name>Krishan Subudhi</name>
  </author>

Refering to the RSS standard to ensure our compliance. the author tag should have an email address:

• https://www.w3schools.com/XML/rss_tag_author.asp
• https://validator.w3.org/feed/docs/rss2.html#hrelementsOfLtitemgt

It'll be natural with the git log, but for the page.meta it's on the page writer.

Originally posted by @Guts in #34 (comment)