bslib theming integration

[cpsievert]

This PR makes it so that, when printed as an HTML table, {gt} will derive CSS defaults from any currently active {bslib} theme (via bs_current_theme()), for example:

library(shiny) library(bslib) library(gt) ui <- fluidPage( theme = bs_theme(bootswatch = "darkly"), gt_output("table") ) server <- function(input, output, session) { output$table <- render_gt({ gt(mtcars) }) } shinyApp(ui, server)

It also works with real-time theming (i.e., add bslib::bs_themer() to the server function above) and rmarkdown+bslib.

[olivroy]

Hi! Would there be interest in reviving this PR?