Add input_check_buttons() and input_radio_buttons()

[cpsievert]

Minimal example:

shinyApp(
    page_fluid(input_check_buttons("foo", c("a", "b", "c"))), 
    function(input, output) { observe(print(input$foo))}
)

This incorporates #484, basically just for documentation purposes (#484 should probably also get merged first).

TODO

• Move inst/component/toggle-buttons.js to TypeScript (i.e., srcts)
• Provide a more scalable layout approach (i.e., grid layout, or even layout_column_wrap()?)
  • Take some inspiration from https://themes.getbootstrap.com/preview/?theme_id=37702 (Shop Women -> Size)
• Should these inputs work without Shiny?
• Is this hack still needed? Or did Bootstrap 5.2 fix the situation?

[CLAassistant]

All committers have signed the CLA.

[cpsievert]

Copy over the relevant params from #484

[cpsievert]

Closing in favor of https://github.com/rstudio/bslib/pull/797/files