Adds to the navigation widget, preserving forward/backward nav, and
inserting a list of clickable page numbers between them.
Phone sized devices continue without this widget as deterministic
display under small screen sizes has not been solved.
The widget is agnostic to the actual amount of pages there are that one
can navigate to and as such shows all plausible, albeit not necessarilly
valid, possibilities.
This widget does not interfere with infinite scroll in any fashion.
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