support for strikethrough, same as GFM (https://help.github.com/articles/github-flavored-markdown/#strikethrough)
support for strikethrough, same as GFM (https://help.github.com/articles/github-flavored-markdown/#strikethrough)

egil/php-markdown-extra-extended,egil/php-markdown-extra-extended,egil/php-markdown-extra-extended