Examine source code of Multiselect for YouTube™

{
  "action": {
    "default_icon": {
      "24": "icons/24.png",
      "48": "icons/48.png"
    },
    "default_popup": "popup.html"
  },
  "author": "Pollux",
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{1b84391e-7c49-4ff3-abab-07bd0a4523e4}",
      "strict_min_version": "109.0"
    }
  },
  "commands": {
    "toggleMultiSelectMode": {
      "description": "__MSG_toggleMultiSelectMode__",
      "suggested_key": {
        "default": "Ctrl+M"
      }
    }
  },
  "content_scripts": [
    {
      "exclude_matches": [
        "https://www.youtube.com/error?*",
        "https://www.youtube.com/howyoutubeworks/*",
        "https://www.youtube.com/intl/*",
        "https://www.youtube.com/kids/*",
        "https://www.youtube.com/live_chat?*",
        "https://www.youtube.com/pop-up-player/*"
      ],
      "js": [
        "js/start.js"
      ],
      "matches": [
        "https://www.youtube.com/*"
      ],
      "run_at": "document_start"
    },
    {
      "css": [
        "css/main.css"
      ],
      "exclude_matches": [
        "https://www.youtube.com/error?*",
        "https://www.youtube.com/howyoutubeworks/*",
        "https://www.youtube.com/intl/*",
        "https://www.youtube.com/kids/*",
        "https://www.youtube.com/live_chat?*",
        "https://www.youtube.com/pop-up-player/*"
      ],
      "js": [
        "js/content.js"
      ],
      "matches": [
        "https://www.youtube.com/*"
      ],
      "run_at": "document_end"
    }
  ],
  "default_locale": "en",
  "description": "__MSG_extensionDescription__",
  "icons": {
    "24": "icons/24.png",
    "48": "icons/48.png",
    "96": "icons/96.png",
    "128": "icons/128.png"
  },
  "manifest_version": 3,
  "name": "__MSG_extensionName__",
  "options_ui": {
    "open_in_tab": true,
    "page": "options.html"
  },
  "permissions": [
    "storage"
  ],
  "version": "3.7",
  "web_accessible_resources": [
    {
      "resources": [
        "js/polymer.js"
      ],
      "matches": [
        "https://www.youtube.com/*"
      ]
    }
  ]
}