Add .asf.yaml file

Documentation branches have to conform to
https://cwiki.apache.org/confluence/display/INFRA/Git+-+.asf.yaml+features\#Git.asf.yamlfeatures-WebSiteDeploymentServiceforGitRepositories
diff --git a/.asf.yaml b/.asf.yaml
new file mode 100644
index 0000000..6e33a03
--- /dev/null
+++ b/.asf.yaml
@@ -0,0 +1,2 @@
+publish:
+    whoami: asf-site