Better Footnote Handling

[almontg]

Default footnote behaviour is clunky and academics will never not use footnotes so very worth addressing.

@hkemp2128 suggested:

perhaps footnote highlighting when clicked, and then a "back to story" button or something? Or like footnote pops up in a little window so you can see reference without losing place in narrative

[garrettdashnelson]

Should not be too difficult with some customizations to the Markdown formatter.