Rendering for footnotes in markdown almost working, misses one character

Footnotes are not officially supported by gitlab since they do not appear in the documentation.

I gave it a try and it actually works, minus a small default: the first [ is not superscripted.

This is a note[^1].

[^1]: my note

renders

This is a note¹.

It would be nice to complete the support for footnotes and to promote it in the documentation.

1. my note ↩