Examine source code of Time To Stretch

{
  "manifest_version": 2,
  "name": "timeToStretch",
  "version": "1.0",
  "homepage_url": "https://github.com/sirector/timeToStretch",
  "icons": {
    "48": "icons/icon2.png"
  },
  "description": "Reminds you to stretch every hour.",
  "permissions": [
    "notifications"
  ],
  "background": {
    "scripts": [
      "index.js"
    ]
  },
  "browser_action": {
    "default_title": "Hourly Check!",
    "default_popup": "index.html"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{c772538a-90fc-4174-9c7d-184ff5444167}"
    }
  }
}