Write instructions for the PDL blogging engine

We have a basic outline in the Author section of the Advent Calendar wiki entry. That should be cleaned up so that a first time blogger has no problems.

This Issue holds the discussion.

• fork the repository https://github.com/PDLPorters/pdlporters.github.com
• create a directory statocles-site/blog/YYYY/MM/slug where YYYY is the year, MM the numerical month and the slug is a very short page identifier
• the article is a file called index.markdown in the directory
  • markdown extensions are not really supported (use 4 space indents for code blocks)
  • there is a block of yaml at the top which holds the metadata. Look at https://github.com/PDLPorters/pdlporters.github.com/blob/master/statocles-site/blog/2024/12/02/cartography/index.markdown for an example
• choose a banner image (banner.jpg/png)
  • we like Creative Commons images with attributions, but it's author's choice
• first time authors should add their bio and avatar url to the bios section of statocles-site/site.yml

A slug should be fewer than 5 words separated by hyphen or underscore.

• write instructions for installing and running statocles locally