this custom tag has the footnote text as a property
when rendered
the custom tag is rendered as incremented numbers (options for different numbering formats: letters, roman numbers, symbols...)
the tooltip has the footnote value (option ?)
all footnote texts are listed, along with their numbers, are visible at the bottom of the text
an anchor links the footnote to the text at the bottom
another anchor, from the number next to the footnote text, sends back to the first occurence of the footnote in the text (to the last clicked one would make even more sense)