Link to foveation settings from VRS page

Author: tetrapod00

tutorials/3d/variable_rate_shading.rst

@@ -87,6 +87,8 @@ Using variable rate shading in Godot
     shading. VRS can be used in both pancake (non-XR) and XR display modes.
 
     The Compatibility renderer does **not** support variable rate shading.
+    For XR, you can use :ref:`foveation level <doc_openxr_settings_foveation_level>`
+    as an alternative.
 
 In the advanced Project Settings, the **Rendering > VRS** section offers settings
 to control variable rate shading on the root viewport:

tutorials/xr/openxr_settings.rst

@@ -163,6 +163,8 @@ If a mode is selected that is not supported by the headset, the first available
   From Godot 4.3 onwards selecting the alpha blend mode will also perform these extra steps.
   This does require the latest vendor plugin to be installed.
 
+.. _doc_openxr_settings_foveation_level:
+
 Foveation Level
 ---------------