[meta] BabylonJS WebXR demos: next steps

[paulrouget]

Turn non-AR demo in AR

• use xr.baseExperience.featuresManager
• use background remover feature
• use plane detection and hit test
• use anchor system (might need a new demo)
• remove floor

Make interactive demos usable without a controler

• pinching to grab the objects (ball in tennis demo for example)
• make teletransportation work (physics demo)

[paulrouget]

See https://github.com/BabylonJS/Babylon.js/pull/7288

For example:

const xrBackgroundRemover = fm.enableFeature(BABYLON.WebXRBackgroundRemover.Name);