This is a replica of shiny::textInput()
with the html input "type"
attribute set to "email" rather than "text".
email_input(inputId, label, value = "", width = NULL, placeholder = NULL)
The input slot that will be used to access the value.
Display label for the control, or NULL for no label.
Initial value.
The width of the input, e.g. '400px'.
A character string giving the user a hint as to what can be entered into the control. Internet Explorer 8 and 9 do not support this option.