use title and url in content explorer overlay when available
ensure content explorer overlay title links show 'external' icon
underline table headers and content-explorer tabs on hover
let filter match body font size
improve and add test for headline, add data for engagement criteria
update engagement criteria for each format
fix filter close button position
update 'about guides' text
include tagline, remove excluded item count, fix styles for graph / table switching
add colour key to graph