`runExample()` improvements

[schloerke]

Prior PR https://github.com/rstudio/shiny/pull/1458 that sparked conversation. (Note: PR closed when HEAD branch was moved.)

Goal

Adopt some plumber::plumb_api() functionality for shiny::runExample():

• Package has value, no example name: Provides all examples for package
• No example name, no package name: Provides all examples for all installed packages
• For now, no edit parameter.
• Printing method
• Use "shiny" as subfolder within inst to distinguish from generically named "examples" folder
  • Keep examples as is. Packages like {shinytest2} depend on it being there.
  • Ask team for new core / bslib examples to fill inst/shiny apps

Code to alter from:

• Original {plumber} PR: https://github.com/rstudio/plumber/pull/631
  • Related follow up PR: https://github.com/rstudio/plumber/pull/736
• Current {plumber} function implementation: https://github.com/rstudio/plumber/blob/e829af6a94380cb897441c1c56129504afb9564f/R/plumb.R#L84-L290

[gadenbuie]

This issue proposes shiny as the directoy

• Use "shiny" as subfolder within inst to distinguish from generically named "examples" folder

In #3917, Karan used shiny-examples

https://github.com/rstudio/shiny/blob/e0d67873830e09465f05925970abc81fb129ca90/R/run-example.R#L80

and I generally agree with him -- but I think we should name this folder examples-shiny.

I think shiny is too generic and there are lots of reasons someone might want to include a bare shiny folder in their package. But examples-shiny sorts with the original examples folder and makes its purpose very clear.

[cpsievert]

I think this can be closed now?

[gadenbuie]

I think this can be closed now?

I thought there was still some planned work around user conveniences. My implementation was kind of bare-bones compared to what Karan had started.