Enhanced UI Component

From @ramiromagno:

An in-package solution for the reproducible code Shiny output

```r
# UI
reproFunctionOutput("code_fn")
# Server  
output$code_fn <- renderReproFunction(summary_tbl)
```

Could include:
- Syntax-highlighted function definition
- Copy to clipboard button
- Download as .R file button
- Optional: "Run with different inputs" widget