update zipline copy with CodePen override warning

seed/challenges/basic-ziplines.json

@@ -55,6 +55,7 @@
         "<span class='text-info'>Bonus User Story:</span> As a user, I navigate to different sections of the webpage by clicking buttons in the navigation.",
         "Don't worry if you don't have anything to showcase on your portfolio yet - you will build several several apps on the next few CodePen challenges, and can come back and update your portfolio later.",
         "There are many great portfolio templates out there, but for this challenge, you'll need to build a portfolio page yourself. Using Bootstrap will make this much easier for you.",
+        "Note that CodePen.io overrides the Window.open() function, so if you want to open windows using jquery, you will need to target invisible anchor elements like this one: <code>&lt;a target='_blank'&rt;</a>.",
         "Remember to use <a href='/field-guide/how-do-i-get-help-when-I-get-stuck' target='_blank'>RSAP</a> if you get stuck.",
         "When you are finished, click the \"I've completed this challenge\" button and include a link to your CodePen. If you pair programmed, you should also include the Free Code Camp username of your pair.",
         "If you'd like immediate feedback on your project, click this button and paste in a link to your CodePen project. Otherwise, we'll review it before you start your nonprofit projects.<br><br><a class='btn btn-primary btn-block' href='https://twitter.com/intent/tweet?text=Check%20out%20the%20project%20I%20just%20built%20with%20%40FreeCodeCamp:%20%0A%20%23LearnToCode%20%23JavaScript' target='_blank'>Click here then add your link to your tweet's text</a>"