make logger optional so code can be re-used for CLI interface

lib/services/ldjson-parser.js

@@ -38,11 +38,14 @@ const parseEventData = (eventData) => {
 }
 
 const parseUsingLDJSONData = (html, { logger }) => {
-  logger.log({
-    message: 'Parsing using LDJSON parser',
-    level: 'info',
-    service: 'parser',
-  })
+  if (logger) {
+    logger.log({
+      message: 'Parsing using LDJSON parser',
+      level: 'info',
+      service: 'parser',
+    })
+  }
+
   try {
     // NOTE: Mobile web should have serialized
     // event info in one of the script tags