Added a warning when an `ARSession` is used in a scene (or scenes), but no providers are selected in XR Plug-in Management for the current build platform.
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Bug Fixes
Updated "[Copying the Camera Texture to a Render Texture when accessing the camera image on the GPU](../manual/index.html#copying-the-camera-texture-to-a-render-texture-when-accessing-the-camera-image-on-the-gpu)" documentation to use a 'Command Buffer' instead of a 'Graphics.Blit()' to fix an issue where blit would not work on certain devices.
Fixed a `NullReferenceException` which would happen if you invoked `ARSession.CheckAvailability()` when the ARSession's GameObject was disabled and had never been enabled.
