v0.2.5

Added

• SharedLimiter: a shareable throttle clock + concurrency semaphore. Give the
  same limiter to every Scraper that talks to one host — via the new
  limiter= constructor argument or adopt_limiter() — and the host-wide
  request rate and in-flight cap are enforced across all of them, while each
  scraper keeps its own cookies, headers, and abort signal.
• Scraper now forwards extra keyword arguments (e.g. limiter=) to the
  underlying ScraperEngine.