[Plugin] AttachedSceneEditor

[manio143]

Attached Scene Editor

This plugin is meant to allow launching the user's game from within the Stride.Editor, such that there's no need for an external scene monitor (like StrideLiveEditor).

To use the plugin we would want to either:

• Provide user with an interface to implement which returns an instance of IGame, OR
• Ask user to select an implementation of GameBase with a new() constructor that would be ran.

The second option may be better, as it allows us to provide the game with a GameContext and potentially render it within an Avalonia controlled window.

Consequently, the plugin would subscribe the NextFrame() async event and rebuild it's view model and refresh the view, accessing the SceneInstance game system for the source of entities.

[manio143]

Requires stride3d/stride#870