More input options

Dear Dean,

I am following your `shinyforms` for quite some time now. In the past I had to tinker in shiny to implement certain apps with surveying capabilities and it was horrible to have to repeat certain chunks while arriving at an app with zero reusability (you have to change the script to change the questions, types, etc.). This is why I think this package is well thought out. To partly reach its potential (google forms capabilities) it needs a wider range of input options.

Fortunately, shiny already has those: multiple choice `radioButtons()` and `checkboxGroupInput()`, dropdown `selectInput()`, date `selectInput()` and `dateRangeInput()`, and linear sliders `sliderInput()`. Do you think these will be available?

Thank you.

Start by reviewing the current input types and how shinyforms maps question definitions to Shiny controls. Compare the requested radioButtons(), checkboxGroupInput(), selectInput(), dateRangeInput(), and sliderInput() options, then define supported question configuration and verify that each renders and returns expected values.

Written by the indexing model from the issue text.