Fix messed up rule insertion method

src/imaprules.lua

@@ -22,7 +22,7 @@ pkg.ADD = function(action, loader)
     local rule = {}
     rule.action = action
     rule.loader = loader or pkg.STATE.loader
-    table.insert(pkg.STATE, rule)
+    table.insert(pkg.STATE.ruleset, rule)
 end
 
 return pkg