Examine source code of niconico loop

{
  "manifest_version": 3,
  "name": "niconico loop",
  "short_name": "niconico loop",
  "description": "ニコニコ動画にて、動画を時間指定して区間ループ再生します。",
  "version": "1.1.3",
  "author": "t4num",
  "homepage_url": "http://www.usamimi.info/~t4number/nnlp/",
  "browser_specific_settings": {
    "gecko": {
      "id": "nnlp@t4number.nnlp.com",
      "strict_min_version": "109.0"
    }
  },
  "content_security_policy": {
    "extension_pages": "script-src 'self'; object-src 'self'"
  },
  "background": {
    "scripts": [
      "js/main.js"
    ]
  },
  "permissions": [
    "contextMenus",
    "scripting",
    "storage",
    "tabs"
  ],
  "host_permissions": [
    "https://www.nicovideo.jp/watch/*"
  ],
  "icons": {
    "16": "icons/icon16.png",
    "128": "icons/icon128.png"
  },
  "web_accessible_resources": [
    {
      "resources": [
        "images/icon.svg",
        "css/nnlp.css",
        "js/nnlp_script.js"
      ],
      "matches": [
        "https://www.nicovideo.jp/*"
      ]
    }
  ]
}