Add tabindex to footnotes

Adding a tabindex to the footnotes makes the footnotes focusable,
showing a blue bounding box around the footnote that's linked to in
most browsers.

Author: jeffkreeftmeijer

ox-html-markdown-style-footnotes.el

@@ -39,7 +39,7 @@
 	      (pcase definition
 		(`(,n ,_ ,def)
 		 (format
-		  "<li id=\"fn.%d\" class=\"footdef\" role=\"doc-footnote\">%s %s</li>\n"
+		  "<li id=\"fn.%d\" class=\"footdef\" role=\"doc-footnote\" tabindex=\"-1\">%s %s</li>\n"
                   n
 		  (org-trim (org-export-data def info))
 		  (format "<a href=\"#fnr.%d\" role=\"doc-backlink\">↩&#65038;</a>" n)))))

ox-html-markdown-style-footnotes.org

@@ -89,7 +89,7 @@ It also uses a backlink with an arrow, which resembles the Markdown tradition:
 <h2 class="footnotes">Footnotes: </h2>
 <div id="text-footnotes">
 <ol>
-<li id="fn.1" class="footdef" role="doc-footnote"><p class="footpara">
+<li id="fn.1" class="footdef" role="doc-footnote" tabindex="-1"><p class="footpara">
 A footnote.
 </p>
 
@@ -236,7 +236,7 @@ The updated copy is defined as ~org-html-markdown-style-footnotes--section~:
 		(pcase definition
 		  (`(,n ,_ ,def)
 		   (format
-		    "<li id=\"fn.%d\" class=\"footdef\" role=\"doc-footnote\">%s %s</li>\n"
+		    "<li id=\"fn.%d\" class=\"footdef\" role=\"doc-footnote\" tabindex=\"-1\">%s %s</li>\n"
                     n
 		    (org-trim (org-export-data def info))
 		    (format "<a href=\"#fnr.%d\" role=\"doc-backlink\">↩&#65038;</a>" n)))))

test.el

@@ -7,7 +7,7 @@
   (let ((org-html-markdown-style-footnotes t))
     (org-html-export-as-html))
   (should (string-match-p
-           "<ol>\n<li id=\"fn.1\" class=\"footdef\" role=\"doc-footnote\"><p class=\"footpara\">\nA footnote.\n</p>\n\n<p class=\"footpara\">\nWith a second paragraph.\n</p> <a href=\"#fnr.1\" role=\"doc-backlink\">↩&#65038;</a></li>\n</ol>"
+           "<ol>\n<li id=\"fn.1\" class=\"footdef\" role=\"doc-footnote\" tabindex=\"-1\"><p class=\"footpara\">\nA footnote.\n</p>\n\n<p class=\"footpara\">\nWith a second paragraph.\n</p> <a href=\"#fnr.1\" role=\"doc-backlink\">↩&#65038;</a></li>\n</ol>"
 	   (with-current-buffer "*Org HTML Export*" (buffer-string))))
   (org-html-markdown-style-footnotes-remove))