Read the feed_author key from a plugin section’s config (mirrors
feed_base_url). Used as the Atom feed’s <author><name>. Returns None
when the key is absent or not a string, in which case the caller defaults to
"Rheo".
Read the feed_base_url key from a plugin section’s config (mirrors epub’s
parse_identifier). Any trailing / is trimmed so callers can join paths
with a single /. Returns None when the key is absent or not a string.
Reload callback type - called by watch loop after successful compilation.
Defined here because it’s only needed by the HTML plugin’s development server.