Add author and editor lists

[GreenXenith]

authors and editors are arrays. Posts should ideally always have at least an authors array.

[rubenwardy]

Probably worth amending articles to use this

[rubenwardy]

I think you need to update the posts to use authors rather than author otherwise existing posts will lose authorship info

Unless Jekyll does this automatically from authors

[GreenXenith]

@rubenwardy Posts are now updated with these fields.

I've opted to exclude listed authors/editors from the contributors list, and I added PR reviewers with minor changes to the contributors list.

The formatting is also a bit nicer now (Written by Name1, Written by Name1 and Name2, Written by Name1, Name2, and Name3), and applied to the contributors list.