Add option to run shine() gadgets as RStudio jobs in the backround

[lianos]

Currently running shine() on a FacileAnalysisResult launches a shiny gadget that will block the R environment.

We should be able to run these gadgets a background jobs within RStudio so that we can have the shiny gadget running while enabling user to still interact with the R console.

[jonocarroll]

Some findings on this after a more recent look around...

It's possible to run a background job shiny app now.

That RStudio feature is only present when developing a standalone app, though. Programatic triggering seems a bit more difficult.

This guide is one approach, though it assumes one can re-write the server. An alternative is rstudioapi::jobRunScript() for which there is a nice wrapper in job(). That requires that one is calling runApp() rather than relying on the default action of shinyApp() but that's a small change.

Using an example in the README, I can trigger fdgeGadget() to be run without blocking the session with

job::job({shiny::runApp(FacileAnalysis::fdgeGadget(samples))})

however, this:

• doesn't launch the browser, likely due to that being controlled by the FacileAnalysis code
• doesn't show the gadgetTitleBar() with 'Cancel'/'Done' buttons since it's not detected as interactive() (and as such needs to be killed to stop it, rather than cleanly returning the results)
• necessarily makes a copy of data in the workspace to be read back in by the spawned process - this might need some finessing.

I suspect these are minor adjustments required, but making background gadgets seems at least possible now.