change redbasic dark schema to make categories and highlights readable

additions to /view/theme/redbasic/schema/dark.css to change the appearance of category badges and highlighted text ([hl]...[/hl]).

hl text changed from master: it's not 'strong' anymore. commented out the pseudo-class selector that works in master but not in dev anymore.

again, i think that using CSS classes would be better than inline style.