Blog: Editoral note

[ryanmacklin]

Is your feature request related to a problem? Please describe.
Related to issue 75, let's have a way to include an editorial note regarding the nature of content that isn't part of the article body flow.

Describe the solution you'd like
Either as body copy with some denotation, or as a separate field in the blog header. Whichever is technically better. (The former allows for editorial notes within flow of text, not just at the top of a page.

Copy would render differently: italicized and starting with "Editorial note: ". We'd be able to have this rendered via Hugo rather than manually in markdown, so we could change the style as needed.

Describe alternatives you've considered
Just doing it manually

Additional context
None