feat: Add Toolbar

[elnelson575]

Fixes #1247

Adds a toolbar that can hold a variety of UI inputs, buttons, and elements.

Toolbars generally contain small versions of inputs meant to fit in the headers/footers of cards, under cards, and other places you might want slimline versions of input components.

Examples:

Card with header toolbar (right), footer toolbar (left), and sub-card footer (left)

Card header: Right aligned
Card footer (only on card 1): Left aligned
Sub-card: Left aligned

library(shiny)
library(bslib)

ui <- page_fillable(
    tags$head(
        tags$link(rel = "stylesheet", type = "text/css", href = "styles.css")
    ),
    card(
        card_header(
            icon("star"),
            "Card 1 header",
            toolbar(
                align = "right",
                actionButton("go", label = "Go", class = "btn-sm"),
                actionButton(
                    "edit",
                    NULL,
                    icon = icon("pencil"),
                    class = "btn-sm"
                ),
                actionButton(
                    "calendar",
                    label = "Schedule",
                    icon = icon("calendar"),
                    class = "btn-sm"
                )
            )
        ),
        p("Card 1 body"),
        sliderInput("slider", "Slider", 0, 10, 5),
        max_height = "500px",
        card_footer(
            toolbar(
                align = "left",
                actionButton(
                    "paragraph",
                    NULL,
                    icon = icon("paragraph"),
                    class = "btn-sm"
                )
            ),
        )
    ),
    toolbar(
        align = "left",
        actionButton("test2", NULL, icon = icon("star"), class = "btn-sm"),
        actionButton("love2", NULL, icon = icon("heart"), class = "btn-sm"),
        actionButton("comment2", NULL, icon = icon("comment"), class = "btn-sm")
    ),
    card(
        card_header(
            "Card 2 header",
            toolbar(
                align = "right",
                downloadLink("download", "Download", class = "btn-sm"),
                selectInput("select", NULL, choices = c("A", "B", "C"))
            )
        ),
        p("Card 2 body"),
        sliderInput("slider2", "Slider", 0, 10, 5),
        max_height = "500px",
        card_footer(
            toolbar(
                align = "right",
                actionButton(
                    "paragraph2",
                    NULL,
                    icon = icon("paragraph"),
                    class = "btn-sm"
                )
            )
        )
    ),
    toolbar(
        align = "left",
        actionButton("test", NULL, icon = icon("star"), class = "btn-sm"),
        actionButton("love", NULL, icon = icon("heart"), class = "btn-sm"),
        actionButton("comment", NULL, icon = icon("comment"), class = "btn-sm")
    ),
)

server <- function(input, output) {}


shinyApp(ui = ui, server = server)

</details>

[CLAassistant]

All committers have signed the CLA.

[gadenbuie]

Awesome, this looks like a good foundation for the rest of the toolbar component work. Just two small things to fixup in the tests and you're ready to merge into the toolbar epic branch.