1 - Change to be made in code

•   In bin/background:
  1. Change var str =""; by your twitch name.
  2. Change the Client-id by your provided by twitch.  
• In manifest.json:
  1. Replace title and description by your.

2 - Change your icon

Go to the img file and replace icon.png with your.

3 - Upload on the store!

And here is your extension is ready!