add js66y

[js66y]

Before submitting this pull request, please go through the checklist below.
If you're doing something in the checklist, put an x inside [ ] so that - [ ] becomes - [x]

• I have added a screenshot from browser with my changes
• There are no errors in the console
• I had fun going through this tutorial (ノ^o^)ノ and learned on the way ٩(＾◡＾)۶
• There are some things I'd like to improve in this tutorial. I have written them below.