Examine source code of Longer in Twitter

{
  "name": "Longer in Twitter",
  "description": "Affiche les TwitLonger directement dans le tweet",
  "version": "2.2.1",
  "manifest_version": 2,
  "content_scripts": [
    {
      "matches": [
        "https://twitter.com/*"
      ],
      "js": [
        "index.js"
      ]
    }
  ],
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": false
  },
  "permissions": [],
  "browser_specific_settings": {
    "gecko": {
      "id": "{5dd690a4-8d02-4b66-8033-ebfa9d3463c4}"
    }
  }
}