document interaction of sycl_ext_oneapi_work_group_scratch_memory with sycl graph

Author: Victor Lomuller

sycl/doc/extensions/experimental/sycl_ext_oneapi_graph.asciidoc

@@ -1977,6 +1977,16 @@ The command submission functions defined in
 link:../experimental/sycl_ext_oneapi_enqueue_functions.asciidoc[sycl_ext_oneapi_enqueue_functions]
 can be used to add nodes to a graph when creating a graph from queue recording.
 
+==== sycl_ext_oneapi_work_group_scratch_memory
+
+The new property defined by
+link:../experimental/sycl_ext_oneapi_work_group_scratch_memory.asciidoc[sycl_ext_oneapi_work_group_scratch_memory]
+cannot be used in graph nodes. A synchronous exception will be thrown with error
+code `invalid` if a user tries to add them to a graph.
+
+Removing this restriction is something we may look at for future revisions of
+`sycl_ext_oneapi_graph`.
+
 == Examples and Usage Guide
 
 Detailed code examples and usage guidelines are provided in the