fix: add micromark parser to markdownlint config

In markdownlint 0.36.0, the support for micromark returned. Adding it in
the config object fixes the error described in [this issue](#7)

The new micromark version changes some previously assumed parser behaviors.
It causes some errors related to nested intentation in HTML snippets.
Since currently there is no need to lint HTML, the tokens related to it
are now ignored.

Introduces a new test verification to prevent an error where `htmlText`
tokens cause other text tokens to appear to be indented