Allows most typical .md formatting (minus some edge cases)
Code blocks also work with highlight.js highlighting support
::id creates an empty div with the id "id"
usage: hgen <input.md> <output.html> <header.html>
header.html is optional and prepends the given html to the output file
linking files also loads the file, ex:
[test](test.js) would link test.js to the file with a <script> tag