Docs: Add about helm-org-ql C-x C-s

Author: alphapapa

README.org

@@ -185,6 +185,8 @@ This command displays matches with Helm.  *Note:* Helm is not a package dependen
 
 Note also that queries in this command are specially handled so that quotes around strings may be omitted for ease of typing.
 
++  Press =C-x C-s= in the Helm session to save the results to an =org-ql-search= buffer.
+
 [[images/helm-org-ql.gif]]
 
 *** org-ql-view