table_preview_dep() returns the htmltools::htmlDependency carrying the
table-preview CSS and JS; build_html_table() attaches it automatically.
table_preview_css() returns the base CSS as an inline
shiny::tags$style for hosts that layer delta CSS on top of it (e.g.
blockr.viz's html table block); it reads the same file the dependency
serves, so there is a single source.
Value
An htmltools::htmlDependency or a shiny::tags$style element.