Examine source code of MediaLoader Customizer

{
  "name": "__MSG_extensionName__",
  "version": "0.0.2",
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "run_at": "document_start",
      "all_frames": true,
      "js": [
        "index.js"
      ]
    }
  ],
  "permissions": [],
  "incognito": "spanning",
  "manifest_version": 2,
  "browser_specific_settings": {
    "gecko": {
      "id": "{16672c9c-a0cc-4261-a554-57d1462d3fed}"
    }
  }
}