Examine source code of Mogswampifier

{
  "manifest_version": 3,
  "author": "Electro",
  "name": "Mogswampifier",
  "version": "1.0",
  "icons": {
    "16": "./icons/icon-16.png"
  },
  "description": "Mog thumbnails",
  "host_permissions": [
    "https://www.youtube.com/*"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "Mogswampifier@gmail.com"
    }
  },
  "content_scripts": [
    {
      "matches": [
        "*://www.youtube.com/*"
      ],
      "js": [
        "content.js"
      ]
    }
  ],
  "web_accessible_resources": [
    {
      "resources": [
        "/images/*.png"
      ],
      "matches": [
        "<all_urls>"
      ]
    }
  ]
}