Add a stand-alone mode for the UI

[ballercat]

Why

Using an extension can be a pain in the corporate world with IT blocking a number of custom extensions in the wild.

What

Add some setting like mode or ui or something that will launch a stand-alone (Electron?) window when jam is invoked with a valid URL. I think the default should still be an extension view. Should be easy enough to implement just render the app in Electron or even use a basic web-server to launch the UI in another window (though I like the elector better I think).