How to add Virtual Reality capabilities to your app?

We need to add an environment and create an XR Experience. This will automaticly add a button to our scene to go into VR mode.
const env = scene.createDefaultEnvironment();
const xr = await scene.createDefaultXRExperienceAsync({
floorMeshes: [env.ground]
});
We can also add the WebXR directly to a loaded model without an environment.
// Async call
BABYLON.SceneLoader.Append("https://www.babylonjs.com/Scenes/Mansion/",
"Mansion.babylon", scene, async function () {
var xr = await scene.createDefaultXRExperienceAsync({floorMeshes: [scene.getMeshByName("Allée")]});
});