Converting edge cases

[ktugan]

Hi. Awesome tool, helped me a lot. I had to do some manual pre-processing to filter out some lines. Thought I share this, I saw that some of them are already posted as issues and filter them out.

1. html links <a> are not converted or dropped. Oftentime used for jumping in the document to other parts.

2. markdown comments are included in the final document. They start with <--

3. When using a code block without any language it should default to none. Otherwise the coloring is for most black, but not for the ones without.