readwright 0.31.0

• because: user request (a reader distilling an EPUB textbook: a formula and TABLE 15-1 set as images vanished silently, one long section crowded out the rest of a multi-section read, and the copyright page lacked authors)
• files: scripts/rw.py (HTMLText.handle_starttag, EPUB metadata, cmd_read, read --each-chars), SKILL.md Distilling a book, ../../tests/test_rw.py, version in the five places
  read --each-chars N cuts each selected section at N characters with its own resume line (--max-chars still caps the total). An <img> alone in a block now prints [image omitted: NAME] or [image: ALT] when the alt text says something; MathML prints [math: ALTTEXT] or [math omitted]. info adds isbn from an ISBN-shaped dc:identifier and decodes entities in the description. Word counts of image-heavy books rise slightly, since the markers count as words.