Allow sorting in org-ql-block

Since this is meant to be used in the agenda, it's useful to see items
sorted by date, deadline, or priority. This commit allows sorting by any
of the methods already implemented in org-ql-select.

org-ql-search.el

@@ -73,6 +73,9 @@
 (defvar org-ql-block-header nil
   "Optional string overriding default header in `org-ql-block' agenda blocks.")
 
+(defvar org-ql-block-sort nil
+  "Optional value or list of Org QL sorting methods (see `org-ql-select').")
+
 ;;;; Customization
 
 (defgroup org-ql-search nil
@@ -246,7 +249,8 @@ automatically from the query."
 			       (narrow-to-region org-agenda-restrict-begin org-agenda-restrict-end))))))
                 (items (org-ql-select from query
                          :action 'element-with-markers
-                         :narrow narrow-p)))
+                         :narrow narrow-p
+                         :sort org-ql-block-sort)))
       (when narrow-p
         ;; Restore buffer's previous restrictions.
         (with-current-buffer from