Some more random copyediting of Hugo docs

Some more random copyediting of Hugo docs

 - Change "livereload" and "live reload" to "LiveReload";
 - Add a `$ ` prompt before example command lines
   (not exhaustive, work in progress);
 - Remove unnecessary whitespace from partials;
 - Revise the blackfriday options table in overview/configuration.md
   to make it narrower.
 - Manually set the language for highlight.js where appropriate
 - Rename "404" to "Custom 404 page", and remove incorrect reference
   to "homepage"
 - Credit the author of tutorials/github_pages_blog.md
   (Similar notes are necessary for other contributed pages where
    "I" am not spf13 to avoid reader confusion.)
 - Add CSS for `kbd` and `table` etc. to css/style.css;
 - etc.