Examine source code of Customizer

{
  "manifest_version": 2,
  "name": "Customizer",
  "version": "0.0.3",
  "author": "Robin van Nunen",
  "description": "Edit any website with your own style.",
  "browser_specific_settings": {
    "gecko": {
      "id": "customizer@vnunen.nl",
      "strict_min_version": "79.0"
    }
  },
  "icons": {
    "48": "img/icon-48.png",
    "128": "img/icon-128.png"
  },
  "browser_action": {
    "default_icon": "img/icon-off-19.png",
    "default_title": "Customizer",
    "default_popup": "popup.html"
  },
  "content_scripts": [
    {
      "matches": [
        "*://*/*"
      ],
      "js": [
        "lib.js",
        "content.js"
      ],
      "run_at": "document_end",
      "all_frames": true
    }
  ],
  "background": {
    "scripts": [
      "lib.js",
      "background.js"
    ],
    "persistent": false
  },
  "permissions": [
    "storage",
    "activeTab",
    "tabs"
  ]
}