Markdown headings can bust to the topmost nav level

[oprypin]

I'm actually not entirely sure if it's the case for Python renderer, but in my own renderer I ran into the issue that if the docstring contains a # Markdown Heading, it's not adjusted according to the current heading_level, so in the nav it'll just appear as a topmost item regardless of what's happening around it.

I'm currently looking into a solution.

[oprypin]

For myself I fixed it in mkdocstrings/crystal@d621b12

Before	After

[pawamoy]

It certainly behaves the same for the Python renderer. I didn't think about using headings in docstrings myself. I'd say it's more a lack of a feature than a bug 🙂
If you want to send a PR with your fix @oprypin, I'll accept it!