Examine source code of ntp_titler

{
  "description": "Adds a title prefix - for the current window based on the type of the active page",
  "author": "MrOtherGuy",
  "manifest_version": 2,
  "name": "ntp_titler",
  "permissions": [
    "tabs",
    "browserSettings"
  ],
  "version": "0.4",
  "background": {
    "scripts": [
      "background-script.js"
    ]
  },
  "applications": {
    "gecko": {
      "id": "ntp_titler@example.com"
    }
  }
}