Reads bslib's dark-mode switch (input[[id]], "dark" or "light"), for
is_dark arguments such as map_sp(), plot_ts(), cc_plotly_theme().
Before the switch has reported (first flush) it is default.
Arguments
- input
the Shiny
inputobject- id
the switch's id, as given to
cc_brand_header()- default
value before the input exists