This is needed until cdnjs figures out their future in
cdnjs/cdnjs#13524. Until then, we will just reference their existence
and promote jsDelivr to the primary source.
This should hopefully fix the issue we were seeing where the docs
would not render properly immediately after a release because CDNjs
has a delay in updating versions. jsdelivr does not have this delay,
so we shouldn't have any many rendering issues.
