cli-v1.10.0

Added

• Markdown import now builds a whole book from a folder or .zip. Point
  epublift import at a directory of Markdown — or a .zip of one — and
  every .md / .markdown file is imported and appended in filename order
  (so 00_…, 01_… chapter prefixes order correctly), instead of just one file.
  Each file is still split at its own top-level # headings.
• Cover image support. A file named cover.png / cover.jpg / cover.webp
  in the folder/zip becomes the EPUB cover (a cover-image manifest entry,
  an EPUB2 <meta name="cover"> fallback, and a cover page first in the spine).
  The cover is re-encoded to WebP when that comes out smaller — the same
  size-safe rule the optimizer uses — so a large source cover doesn't bloat the
  book. See docs/markdown-import.md.

Fixed

• Zip import no longer drops all but one chapter. Previously a .zip of
  several .md files imported only the shallowest single file (and ignored any
  cover); a 10-chapter book came out as one. All files are now combined.

Full Changelog: cli-v1.9.0...cli-v1.10.0