Examine source code of FD transparent

{
  "manifest_version": 2,
  "name": "FD transparent",
  "version": "3.0.1",
  "description": "Ajoute un bouton pour activer et désactiver la transparence des images sur le Forum Dessiné (https://forum-dessine.fr).",
  "icons": {
    "48": "icon48.png",
    "96": "icon96.png"
  },
  "content_scripts": [
    {
      "matches": [
        "*://*.forum-dessine.fr/*"
      ],
      "js": [
        "content.js"
      ]
    }
  ],
  "background": {
    "scripts": [
      "permissions.js",
      "background.js"
    ]
  },
  "permissions": [
    "storage",
    "*://*.forum-dessine.fr/*"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{9bf41bb9-68ed-49b8-9866-5caf0725e153}"
    }
  }
}