Add example app throughout the course

[StatsRhian]

I find it's helpful to have a single shiny application which is built throughout the course so learners can see the concepts introduced on a real example.

Data set

Probably something from {NHSRdatasets} or NHS workforce statistics (which I may add to {NHSRdatasets}

Building it up

• Add the layout (sidebar with title)
• Add the inputs
• Add the outputs (table & a plot)
• Change so it uses reactive()
• ? Use actionButton() and eventReactive() or bindEvent() to change reactive graph
• Add styling with {bslib} (valuebox?)
• Move any R code into functions sourced via R/
• Deploy to shinyapps.io