docs: import virgl docs

The docuentation has been imported verbatim from
https://virgil3d.github.io/.

Acked-by: Chia-I Wu <olvaffe@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/13836>

docs/systems.rst

@@ -32,8 +32,8 @@ Layered driver include:
 -  :doc:`D3D12 <drivers/d3d12>` - driver providing OpenGL on top of
    Microsoft's Direct3D 12 API.
 -  :doc:`SVGA3D <drivers/svga3d>` - driver for VMware virtual GPU
--  `VirGL <https://virgil3d.github.io/>`__ - research project for
-   accelerated graphics for qemu guests
+-  `VirGL <drivers/virgl>` - research project for accelerated graphics
+   for qemu guests
 -  :doc:`Zink <drivers/zink>` - driver providing OpenGL on top of
    Khoronos' Vulkan API.