docs: add link to extension spec

We already do this for all the other VK extensions, so we might as well
do this for VK_EXT_vertex_attribute_divisor as well.

Fixes: 2ff97847d19 ("docs: document zink's gl > 3.0 requirements")
Reviewed-By: Mike Blumenkrantz <michael.blumenkrantz@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/7312>
diff --git a/docs/drivers/zink.rst b/docs/drivers/zink.rst
index 974a82f..e39ad3b 100644
--- a/docs/drivers/zink.rst
+++ b/docs/drivers/zink.rst
@@ -86,7 +86,7 @@
 
 * Device extensions:
 
-  * ``VK_EXT_vertex_attribute_divisor``
+  * `VK_EXT_vertex_attribute_divisor`_
 
 Debugging
 ---------
@@ -131,3 +131,4 @@
 .. _VK_KHR_external_memory: https://www.khronos.org/registry/vulkan/specs/1.2-extensions/man/html/VK_KHR_external_memory.html
 .. _VK_EXT_transform_feedback: https://www.khronos.org/registry/vulkan/specs/1.2-extensions/man/html/VK_EXT_transform_feedback.html
 .. _VK_EXT_conditional_rendering: https://www.khronos.org/registry/vulkan/specs/1.2-extensions/man/html/VK_EXT_conditional_rendering.html
+.. _VK_EXT_vertex_attribute_divisor: https://www.khronos.org/registry/vulkan/specs/1.2-extensions/man/html/VK_EXT_vertex_attribute_divisor.html