* craft-epub: read EPUB 2 and 3 packages (container, package document, bounded entry reads)
The container layer of WordCraft's EPUB import (storytold/wordcraft#3119): container.xml,
the package document's metadata, manifest and spine, href resolution, and entry reads inside
per-entry and total byte budgets. Moved onto craft-xml, read strictly, and extended to EPUB 2
packages (NCX path, cover meta, dc-metadata).
* craft-epub: write EPUB 3 packages (reflowable and fixed layout)
The packaging of DesignCraft's EPUB export (crates/epub/src/package.rs at 513f77b8): the stored
mimetype, container, package document, nested navigation, fixed-layout metadata and the
derived identifier, behind a neutral Book of metadata, resources, spine and navigation. Adds
the dc:subject and dc:description metadata, the W3CDTF check and the stricter language tag
check of WordCraft's EPUB export (storytold/wordcraft#2815).
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Co-authored-by: Michael <monashmichaelmu@gmail.com>
