Trying to use footer argument in bslib::navset_card_tab()

[drfinlayscott]

Hi,
I'm trying to use the 'footer' argument of a bslib::navset_card_tab but don't really know what I'm doing. I would like some text to appear at the bottom of the navset_card_tab for every tab (ideally, I would also like a popover but I'm starting small).

The footer argument has the documentation:

UI element(s) (tags) to display below the nav content.

My simple attempt is shown here. No footer appears. I've tried using other tag types but still no joy. Can anyone help?

Thanks

library(shiny)
library(bslib)

ui <- page_sidebar(
  title = "Test dashboard",
  navset_card_tab(
    title="Demo",
    # I would like a footer at the bottom of the navset_card_tab.
    # Trying to use the footer argument but not sure how to use it.
    footer = tags$p("Footer test"),
    nav_panel("Plot 1", plotOutput("plot1")),
    nav_panel("Plot 2", plotOutput("plot2"))
  )
)

server <- function(input, output) {
  output$plot1 <- renderPlot(plot(1:10))
  output$plot2 <- renderPlot(plot(20:21))
}

shinyApp(ui, server)