A minor release, delivering minor fixes since the last release, and resolving ambiguity in the README about the import path for blackfriday v2:

• Committed to github.com/russross/blackfriday/v2 as the canonical import path for blackfriday v2. (Issue #587)
• Added HTML_NOOPENER_LINKS HTML renderer option. (Issue #459, PR #570)
• Fixed parsing of fenced code blocks inside lists. (Issues #495 and #485, PR #521)
• Fixed an issue where <details> tag was wrapped in <p> tag. (Issue #525, PR #559)
• Fixed parsing of links that end with a double backslashes. (PR #512)