Examine source code of Get Text Info

{
  "manifest_version": 2,
  "name": "Get Text Info",
  "version": "1.0",
  "description": "Retrieves information about the selected text.",
  "permissions": [
    "activeTab",
    "contextMenus",
    "storage"
  ],
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": false
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content.js"
      ]
    }
  ],
  "browser_action": {
    "default_popup": "popup.html",
    "default_icon": {
      "16": "icon.png",
      "48": "icon.png",
      "128": "icon.png"
    }
  },
  "options_ui": {
    "page": "options.html",
    "open_in_tab": true
  },
  "applications": {
    "gecko": {
      "id": "gettextinfo@example.com"
    }
  }
}