Update .asf.yaml

Link to user doc
diff --git a/.asf.yaml b/.asf.yaml
index 776b8c2..c9c5922 100644
--- a/.asf.yaml
+++ b/.asf.yaml
@@ -1,3 +1,4 @@
+# See: https://cwiki.apache.org/confluence/display/INFRA/git+-+.asf.yaml+features
 github:
   features:
     # Enable issue management