0.8.4

Added

• Books and audiobooks from your download sources. A plugin can now ask
  the app to download a book or audiobook (api.downloadMedia) and the same
  sources that serve comics go looking: usenet and torrent search the book
  and audiobook categories with a matcher built for how book releases are
  named (author and title, no issue number; the right kind of file), and a
  site source takes part when its definition declares types: ['ebook'] or
  ['audiobook']. The plugin that owns the library type files the result
  (api.registerMediaHandler) and whoever asked is told when it lands
  (api.onMediaDownload). The Requests plugin uses this to fill approved
  book requests. A book with an ISBN is asked for by ISBN first on catalog
  sites, so the exact edition wins over a look-alike. A site source may
  verify what it downloaded and refuse it (an EPUB whose own metadata
  says it is a translation, say); the next-best candidate is tried.

• Sites behind DDoS-Guard. Its interstitial is recognised as a challenge,
  a FlareSolverr "solve" that hands back the interstitial (the manual captcha
  it escalates headless browsers to) is reported as one rather than parsed
  as a page, and once the app's own browser clears a site, its cookies are
  reused for plain requests to it. A site source can mark a setting
  secret: true to have it masked on its card.

• Books and audiobooks show in the queue. A book being searched for,
  downloaded by a site source, or fetched by a download client is a row on
  the Queue page with its source and progress, counts toward the sidebar
  badge, and can be cancelled while a client has it. The log says which
  source was searched, what release was picked, and what was filed.

• Add finds books and audiobooks. With a Books or Audiobooks library
  (and its plugin), the Add button gains a tab for it: search the catalog,
  see what is already on the shelf, add one and the download sources are
  asked for it.

Fixed

• One browser per process: a site source that needs the browser now shares
  the one a plugin already launched instead of starting a second Chromium
  on the same profile, which Chromium refuses ("Opening in existing browser
  session").