* fix(theme/index): Use nav element for Table of Content
* fix(renderer/html_handlebars/helpers/toc): Use ol instead of ul
Chapters and sections are ordered, so we should use the appropriate HTML tag.
* fix(renderer/html_handlebars/helpers/toc): Hide section number from screen readers
Screen readers have this functionality build-in, no need to present this. Ideally, this should not even be in the DOM tree, since the numbers can be shown by using CSS.
* fix(theme/index): Remove tabIndex="-1" from .page
Divs are not focusable by default
* fix(theme): Make sidebar accessible
Using aria-hidden (together with tabIndex) takes the links out of the tab order.
http://heydonworks.com/practical_aria_examples/#progressive-collapsibles
* fix(theme/index): Wrap content inside main tag
The main tag helps users skip additional content on the page.
* fix(theme/book): Don't focus .page on page load
The main content is identified by the main tag, not by auto-focusing it on page load.
* fix(theme/index): Make page controls accessible
* fix: Make theme selector accessible
- Use ul and li (since it is a list)
- Add aria-expanded and aria-haspopup to the toggle button
- Use button instead of div (buttons are accessible by default)
- Handle Esc key (close popup)
- Adjust CSS to keep same visual style
* fix(theme/stylus/sidebar): Make link clickable area wider
Links now expand to fill the entire row.
* fix(theme): Wrap header buttons and improve animation performance
Previously, the header had a fixed height, which meant that sometimes the print button was not visible. Animating the left property is expensive, which lead to laggy animations - transform is much cheaper and has the same effect.
* fix(theme/stylus/theme-popup): Theme button inherits color
Bug introduced while making the popup accessible
* fix(theme/book): Handle edge case when toggling sidebar
Bug introduced when switching from animating left to using transform.
