Improve Jira Markdown parser
In !27201 (merged) we introduce a parser that parser Jira Markdown to GitLab Markdown.
There are at least 2 tags that need to be improved:
- code blocks - right now the tags inside code blocks are not ignored - eg. if there is
h1. headerin jira code block it is transfered to
# header. We should ignore jira tags inside the code blocks
- attachments - we don't handle attachments in the first iteration of the parser