Fix Issue fniessen#98

When elements in the table of contents are clicked in readtheorg
theme, the children are toggled.

styles/readtheorg/js/readtheorg.js

@@ -1,3 +1,23 @@
+function collapse_toc_elements_on_click (nav_li_a){
+    /*
+      When an `a' element in the TOC is clicked, it's  parent
+      `li' element's active attribute is toggled. This causes
+      the element to toggle between minimized and maximized
+      states. The active attribute is documented in bootstrap.
+      https://getbootstrap.com/docs/4.0/components/navbar/#nav
+    */
+    $(nav_li_el).parent().toggleClass("active");
+}
+
+$( document ).ready(function() {
+    // when the document is loaded and ready, bind the
+    // function `collapse_toc_elements_on_click' to the
+    // `a' elements in the table of contents.
+    $("#text-table-of-contents a").click(function() {
+	collapse_toc_elements_on_click(this);
+    });
+});
+
 $(function() {
     $('.note').before("<p class='admonition-title note'>Note</p>");
     $('.seealso').before("<p class='admonition-title seealso'>See also</p>");