Handle markdownlint-disable-file before file parsing

[3y3]

markdownlint can handle special comment for lint disabling

<!-- markdownlint-disable-file -->

If file is very big this slows down file processing - we need to tokenize all file data and then drop this tokens, because first token is special comment.

So, best strategy will be to handle this comment manually or to add optimistic check to markdownlint itself.