Preview button shows wrong location when story outside the plugin window

[Billy Snikkers]

To recreate, open a story and click the UI floating button to put it into the viewport (sorry if that's not what it's called), then click the Preview button. The result is that it selects the location in the explorer (inside PluginService) where it would be if the story was inside the plugin window, instead of CoreGui.Hoarcekat display where it actually is.

Also I didn't see it noted anywhere that "Show Plugin Gui Service" had to be checked in studio settings for the preview button to work. Maybe this could be added to the README (plus the setting to show CoreGui).

[boyned//Kampfkarren]

We can check if you have the setting enabled through settings() and throw a warning otherwise.