Add milestone config for labeler (#3546)

Author: Thraka

.ghal.rules.json

@@ -21,5 +21,12 @@
         }
       }
     }
+  },
+  "pullrequest": {
+    "opened": {
+      "processor-default": {
+        "milestone-set": "November 2019"
+      }
+    }
   }
 }