reveal.js 3.7.0 on Node.js Yarn

Changes:

Key Binding API (#1885 by @ denehyg)
Adds pdfSeparateFragments option for exporting fragments on separate PDF pages (@koehlma)
Adds fragmentInURL option for including fragments in the URL (@dougalsutherland)
Adds hashOneBasedIndex option for switching slide URLs from 0 to 1-based index (@sean-parent)
Adds data-background-opacity attribute for fading out background media
Adds a "Resume presentation" button to the pause overlay
Adds two new fragment styles
- semi-fade-out: starts fully visible and fades out to 50% opacity
- fade-in-then-semi-out: fades in like a normal fragment and remains visible but faded out when you move to the next fragment
New API method Reveal.syncSlide: same use as Reveal.sync but more efficient when you've only made changes to one specific slide
New API method Reveal.syncFragments: same use as Reveal.sync but more efficient when you've only made changes to fragments on one specific slide
Removes arbitrary restrictions on slide IDs, all IDs are now valid
The slide number is now an anchor pointing to the current hash, making it possible to copy the current slide URL even when history is disabled (#2133 by @sean-parent)
Whitespace is now allowed in background image names (@RobertBaron)

Bug fixes:

The left/right navigation arrows no longer appear when there are no horizontal slides
Navigating to the same slide twice in a row no longer drops its "present" class
The loop option now works correctly in presentations with only vertical slides
More graceful error handling of duplicate slide IDs
Interactive iframe backgrounds now work in vertical slides