v0.4.0 — Markdown in the chat

Added

• Real Markdown in the chat. Replies now render headings, tables, nested
  and ordered lists, blockquotes, task lists, strikethrough and reference
  links with markdown-it (vendored, pinned, verified against npm). Code fences
  get a language banner, a Copy button and syntax colours from Prism for 12
  common languages. Full web addresses (http or https) and email addresses
  in a reply become links; bare domains and file names such as setup.py
  do not. Links stay limited to http, https and mailto, images never load
  (one shows as an [image: alt text] marker), and raw HTML stays plain
  text, so the chat still never loads anything from the web. Single line
  breaks still break lines. Thanks @kurotope.
  (#6)

• read_page lists custom comboboxes. ARIA comboboxes (role="combobox"
  on a div or similar) now appear in the page map with their label and the
  option currently shown, so the agent can open them and pick an option, as it
  already could with <select>. A <textarea role="combobox"> keeps reporting
  what was typed into it. Thanks @reopenpilot.
  (#5)

Changed

• Contributing rules. No npm runtime dependencies still holds; a library
  may be vendored case by case when it is pinned, byte-verified against the
  official npm package, and shipped with its license. See CONTRIBUTING.md.

Fixed

• click_element fired twice. The content script dispatched a synthetic
  click and then also called el.click(), so the element's default action ran
  two times: checkboxes flipped straight back, and forms with a JavaScript
  submit handler submitted twice. Now exactly one click fires. double_click
  sends two, as a native double-click does. Thanks @reopenpilot.
  (#4)