Auto-hide navigation on link click

Hide navigation sidebar when clicking anchor links on mobile devices.
Previously, anchor links would change the page but the navigation
sidebar would block the view.

Author: sunblaze

lib/rdoc/generator/template/darkfish/js/darkfish.js

@@ -106,9 +106,22 @@ function hookSidebar() {
   }
 }
 
+function hookAnchorLinks() {
+  document.addEventListener('click', (e) => {
+    const anchor = e.target.closest('a[href^="#"]');
+    if (anchor && window.matchMedia("(max-width: 1023px)").matches) {
+      const navigation = document.querySelector('#navigation');
+      const navigationToggle = document.querySelector('#navigation-toggle');
+      navigation.hidden = true;
+      navigationToggle.ariaExpanded = false;
+    }
+  });
+}
+
 document.addEventListener('DOMContentLoaded', function() {
   hookSourceViews();
   hookSearch();
   hookFocus();
   hookSidebar();
+  hookAnchorLinks();
 });