Refactor 'preprocess-*' and 'generate-news' into around-like functions
All preprocess-* functions are now called "around" the original renderer, instead of in separate passes. This approach facilitates passing information between each of the processing steps. The major driver for this change is the need to pass around the original file name, which we need to generate the
Edit this page button.
Introduce a way to declare dependencies between pages. That way, we can convert
generate-news into a post-processor for
news.md, delaying the rendering of
news.md has been generated.
And last but not least: actually add the 'Edit this page' button with a link to our GitLab project!
Closes #8 (closed).