Markdig 0.12.3

> 0.12.3 - Fix issue with HTML blocks for heading h2,h3,h4,h5,h6 that were not correctly identified as HTML blocks as per CommonMark spec > 0.12.2 - Fix issue with generic attributes used just before a pipe table (issue #121) > 0.12.1 - Fix issue with media links extension when a URL to video is used, an unexpected closing `</iframe>` was inserted (issue #119) > 0.12.0 - Add new extension JiraLink support (thanks to @clarkd) - Fix issue in html attributes not parsing correctly properties (thanks to @meziantou) - Fix issues detected by an automatic static code analysis tool > 0.11.0 - Fix issue with math extension and $$ block parsing not handling correctly beginning of a $$ as a inline math instead (issue #107) - Fix issue with custom attributes for emphasis - Add support for new special custom arrows emoji (-> <- <-> <= => and <==>)