Improve formatter and update `auto_linker`

This MR updates auto_linker dependency and improves markdown parsing: now it escapes mentions, then parses markdown and then adds links.

Notable changes in auto_linker:

• Fix parsing HTML tags without attributes: <div class='section'>google.com</div> did work but <div>google.com</div> didn't.
• Fix parsing inside nested HTML (<p><strong>google.com</strong></p>)
• Do not parse inside <pre> and <code> (close #795 (closed) )
• Improve TLD lookup performance (auto_linker!13)
• Add more tests (test coverage is 100% now)