Add a command for extension authors to test their extension in the editor

[riknoll]

This will require some Heavy Witchcraft but it would be extremely useful to be able to test extensions in the arcade editor just like you can with the github experience in MakeCode

[jwunderl]

Other than hacking this in by generating a share link and having it load that, any chance we could implement this by popping open a webview and messaging it in just like https://makecode.com/playground in controller mode?

[riknoll]

yeah, that was what i was thinking as well! should be able to do it with a webview easily enough