Examine source code of Twitterify

{
  "manifest_version": 2,
  "name": "Twitterify",
  "version": "1.0",
  "description": "replaces every instance of the letter \"x\" with the word \"twitter\". no exceptions",
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "twitterify.js"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{30520e3b-f7cc-4beb-ad75-de357ef42776}"
    }
  }
}