Add a "stop" button

[oranwutang]

Hi there!

One of the best uses that I can see for webR is for using it on mobile devices or tablets, recently I was running a script, on your webR REPL demo, that makes an animated plot with the {tourr} package (something simple like tourr::animate_xy(tourr::flea[, 1:6]) ). The thing is that in order to stop the animation the console asks for pressing the escape key, which obviously is lacking on the iPad.

A nice solution would be to have a "stop" button like the one in rstudio that lets you break the current R process.

So I'm asking for you to add such button to the GUI.

I don't know if this is the best place for this request, please let me know if it should be posted in other place.

Thanks in advance!

Best regards