4.2.0
update presentation examples move to root @ /examples
Fix unmatched h3-tags
polyfill element.closest for ie11
fix broken asset urls in examples
Fix copy/paste-o
katex math rendering; fix broken 2477 delimiter, compatibility with external markdown #2559
copy
bg videos remain muted on mobile, otherwise broken when navigating with swipe gestures
move highlight themes from lib/css/ to plugin/highlight/