[Feature] Plugin/mod support

[Durtur]

Add support for 3rd party widgets. They should be dynamically displayed in the main app screen, in an electron webview or iframe and should navigate to a website or html file that is the plugin UI.

For security reasons the main window should be refactored with context isolation in mind, to prevent unfettered access to nodejs and the file system.

Maybe add a basic API for the widgets to use.