Heading footnotes don't render properly in markdown files

[gregsadetsky]

Footnotes work really well![^1]

and they work in headings as well[^2]

unfortunately, the same markup as above in a markdown file looks like this:

it would be great if the markdown file rendering could also include the <sup> tag :-)

thank you!

[^1]: they really do! [^2]: that's cool