Change this selector to use the ~= selector to test if a white space
separated word "prev" or "next" is contained
Fixes a speaker notes bug that did not allow going to the next slide in
the speaker notes.
The reason for that is that the "rel" attribute contained "prev"
respective "next prefetch".
See:
https://developer.mozilla.org/en-US/docs/Web/CSS/Attribute_selectors#attrvalue_2
This fixes part of #2004 when going to the right (containing
"prefetch").
* Add chrome.css and general.css to override default css file. This is
necessary to fix links without underline (hyperlinks relying only on
color).
* Fix pop-out button without id and wrong ARIA-ROLE
* Speaker's notes now at correct heading sequence (H3)
