Examine source code of Custom Site JS

{
  "manifest_version": 2,
  "name": "Custom Site JS",
  "version": "1.0.1",
  "description": "Run your own (per url or domain) custom JavaScript on sites.",
  "icons": {
    "16": "image/icon16.png",
    "32": "image/icon32.png",
    "48": "image/icon48.png",
    "64": "image/icon64.png",
    "128": "image/icon128.png"
  },
  "browser_action": {
    "default_icon": {
      "16": "image/icon16.png",
      "32": "image/icon32.png",
      "48": "image/icon48.png",
      "64": "image/icon64.png",
      "128": "image/icon128.png"
    },
    "default_popup": "html/index.html"
  },
  "background": {
    "scripts": [
      "js/background.js"
    ],
    "persistent": false
  },
  "permissions": [
    "webNavigation",
    "storage",
    "tabs",
    "*://*/*"
  ]
}