Update style of auto-generated `docs_info` markdown string

[tcompa]

          > If we can also adapt to not show the titles quite so large or not default to setting titles based on docstring info parsed at all

If the user provides a full string, then that one will fully override the original one.
As per the current automatically-generated ones, I'll change the style of the generated markdown.

Originally posted by @tcompa in #874 (comment)

[jluethi]

Let's tackle this one we know how #874 is solved & we handle the layout for that

[tcompa]

This is how the new modal based on #874 would look like, in its current version:

[jluethi]

That's great. I guess it will be useful to highlight some key words in bold, but otherwise makes sense to me :) And with those smaller headers, I'm fine with it