Allow per page/section override of markdown config options

I’m currently working out a way of adding a ‘nofollow’ to the links on a privacy policy but it seems the only way to do it right now is at a global level.

It would be great if we could have a per page/section override of the markdown options. The way I imagine it would work is an additional [markdown] section in the front matter that overrides whatever you have set in your global config for that particular page.