Examine source code of TranslateToEnglish

{
  "manifest_version": 2,
  "name": "TranslateToEnglish",
  "version": "0.1.1",
  "description": "Translate to English",
  "icons": {
    "16": "images/t-16.png",
    "32": "images/t-32.png",
    "48": "images/t-48.png",
    "128": "images/t-128.png"
  },
  "browser_action": {
    "browser_style": true,
    "default_icon": {
      "16": "images/t-16.png",
      "32": "images/t-32.png",
      "48": "images/t-48.png",
      "128": "images/t-128.png"
    },
    "default_title": "Translate to English",
    "default_popup": "index.html"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "translatetoenglish@example.com"
    }
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "inject.js"
      ]
    }
  ],
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": false
  },
  "permissions": [
    "contextMenus",
    "storage",
    "<all_urls>"
  ]
}