Closes #188 - change target to id in showPopover example code

[andrewbaxter439]

Closing issue #188 in hopefully a simple manner. New example function works as expected:

ui <- container(
  buttonInput("showHelp", "Help!"),
  div(
    id = "textBlock1",
    "Sociis natoque penatibus et magnis"
  ) %>%
    padding(3)
) %>%
  display("flex") %>%
  flex(justify = "around")

server <- function(input, output) {
  observeEvent(input$showHelp, ignoreInit = TRUE, {
    showPopover(
      id = "textBlock1",
      popover(title = "Hint", "I am a <div> element!"),
      placement = "bottom",
      duration = 4
    )
  })
}

shinyApp(ui, server)