Extensibility

[JaiganeshKumaran]

Implement app extensions for extending Develop's capabilities. I'm planning on three types of extensions for now:

• Code editor plugins: Plugins that integrate specifically with the code editor. Can be either a background service (eg: language server) or a plugin with a UI
• Project view plugins: Extends the project view with more features
• Template plugins: Provides project and item templates

The same app should be able to provide multiple plugins. App Service will be used for communication however we should provide a wrapper Windows Runtime API to simplify the developer's work.