message: fix: back button z-index.
diff: @@ -343,12 +343,11 @@ var side_bar = false; // collapse the side bar menu by default.
  nav.css('top', '0');
  nav.css('right', '0');
  nav.css('text-align', 'right');
  - nav.css('z-index', '100');
  + nav.css('z-index', '1000'); // ensures it sits on top of any mdbook menu bar.
  nav.prependTo($('body'));
  const navDiv = $('<span>');
  navDiv.css('padding', '4px');
  navDiv.css('padding-right', '20px');
  - navDiv.css('z-index', '100');
  navDiv.css('background-color', 'var(--vscode-tab-activeBackground)');
  nav.append(navDiv);
  const fontSize = workspace.getConfiguration('editor').get('fontSize') + 'px';
  