Remove 3.x VR tutorials, add landing page for future XR docs (godotengine#5479)

Co-authored-by: Hugo Locurcio <[email protected]>

Author: m4gr3d

about/list_of_features.rst

@@ -495,9 +495,12 @@ Mobile
 XR support (AR and VR)
 ^^^^^^^^^^^^^^^^^^^^^^
 
+- Out of the box support for OpenXR.
+
+   - Including support for popular headsets like the Meta Quest and the Valve Index.
+
 - Support for ARKit on iOS out of the box.
-- Support for the OpenXR and OpenVR APIs.
-- Popular VR headsets like the Oculus Quest and HTC Vive are supported thanks to plugins.
+- Support for the OpenVR APIs.
 
 GUI system
 ^^^^^^^^^^

index.rst

@@ -111,7 +111,7 @@ The main documentation for the site is organized into the following sections:
    tutorials/scripting/index
    tutorials/shaders/index
    tutorials/ui/index
-   tutorials/vr/index
+   tutorials/xr/index
 
 
 .. toctree::