* lisp/ox-md.el (org-md--headline-title): New function.
(org-md-headline): Use `org-md-headline-title' to generate section
headers.
(org-md--footnote-formatted): New function.
(org-md--footnote-section): New function.
(org-md-inner-template): Update to use `org-md-footnote-section'.
(org-md-footnotes-section): New customizable variable.
(org-md-footnote-format): New customizable variable.
Update ox-md.el to export the Footnotes section as Markdown, using HTML
only where necessary - namely, in footnote and footnote reference links.
d4a073f5be