docs: Add release notes for v5.0.0a21

DIRACGrid CI · DIRACGrid CI · commit f131bacf5e31 · 2022-08-04T07:47:44.000Z
diff --git a/release.notes b/release.notes
@@ -1,3 +1,6 @@
+[v5.0.0a21]
+
+
 [v5.0.0a20]
 
 FIX: (#677) set correct argument type for _expand
