dropdown_input: Create dropdown Semantic UI component
In shiny.semantic: Semantic UI Support for Shiny

This creates a default *dropdown_input* using Semantic UI styles with Shiny input. Dropdown is already initialized and available under input[[input_id]].

dropdown_input(
  input_id,
  choices,
  choices_value = choices,
  default_text = "Select",
  value = NULL,
  type = "selection fluid"
)

`input_id`	Input name. Reactive value is available under input[[input_id]].
`choices`	All available options one can select from.
`choices_value`	What reactive value should be used for corresponding choice.
`default_text`	Text to be visible on dropdown when nothing is selected.
`value`	Pass value if you want to initialize selection for dropdown.
`type`	Change depending what type of dropdown is wanted.

## Only run examples in interactive R sessions
if (interactive()) {
library(shiny)
library(shiny.semantic)
ui <- semanticPage(
  title = "Dropdown example",
  dropdown_input("simple_dropdown", LETTERS, value = "A"),
  p("Selected letter:"),
  textOutput("dropdown")
)
server <- function(input, output) {
  output$dropdown <- renderText(input[["simple_dropdown"]])
}

shinyApp(ui = ui, server = server)
}