Add user-agent blocking for dealing with webscrapers

Change-Id: I9c26791a9f96bb2e87f0f427f7ff4adcb46a2b9e
diff --git a/defaults/main.yml b/defaults/main.yml
index 70e2731..14ee763 100644
--- a/defaults/main.yml
+++ b/defaults/main.yml
@@ -39,3 +39,6 @@
 
 # authentication scope dict to create htpasswd files - see README.md
 auth_scopes: {}
+
+# block specific user agents (webscrapers)
+blocked_user_agents: "DotBot|MJ12bot|SemrushBot|PetalBot|AhrefsBot"