Examine source code of Track it!

{
  "manifest_version": 2,
  "name": "__MSG_extName__",
  "homepage_url": "https://github.com/mornir/track-it",
  "default_locale": "en",
  "permissions": [
    "history",
    "storage"
  ],
  "icons": {
    "16": "icons/clock_16.png",
    "32": "icons/clock_32.png",
    "48": "icons/clock_48.png",
    "128": "icons/clock_128.png"
  },
  "browser_action": {
    "default_popup": "popup.html",
    "default_title": "__MSG_extName__",
    "default_icon": {
      "16": "icons/clock_16.png",
      "32": "icons/clock_32.png"
    }
  },
  "options_ui": {
    "page": "options.html"
  },
  "version": "0.2.0",
  "description": "Web extension to track time wasted on addictive websites",
  "content_security_policy": "script-src 'self' ; object-src 'self'"
}