Examine source code of Custom Dark Background

{
  "manifest_version": 2,
  "name": "Custom Dark Background",
  "version": "1.1",
  "description": "Change the background color to the color of your choice.",
  "browser_action": {
    "default_title": "Custom Dark Background",
    "default_popup": "popup/popup.html"
  },
  "permissions": [
    "storage"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "custom-dark-background@cosmow22.fr",
      "data_collection_permissions": {
        "required": [
          "none"
        ],
        "optional": []
      }
    }
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "css": [
        "css/common.css"
      ],
      "js": [
        "script.js"
      ]
    },
    {
      "matches": [
        "*://*.youtube.com/*"
      ],
      "css": [
        "css/youtube.css"
      ]
    },
    {
      "matches": [
        "*://*.chatgpt.com/*"
      ],
      "css": [
        "css/chatgpt.css"
      ]
    },
    {
      "matches": [
        "*://*.mail.google.com/*"
      ],
      "css": [
        "css/gmail.css"
      ]
    },
    {
      "matches": [
        "*://*.qwant.com/*"
      ],
      "css": [
        "css/qwant.css"
      ]
    },
    {
      "matches": [
        "*://*.google.com/*"
      ],
      "css": [
        "css/google.css"
      ]
    },
    {
      "matches": [
        "*://*.radiofrance.fr/*"
      ],
      "css": [
        "css/radiofrance.css"
      ]
    },
    {
      "matches": [
        "*://*.github.com/*"
      ],
      "css": [
        "css/github.css"
      ]
    },
    {
      "matches": [
        "*://*.twitch.tv/*"
      ],
      "css": [
        "css/twitch.css"
      ]
    },
    {
      "matches": [
        "*://*.fr.wikipedia.org/*"
      ],
      "css": [
        "css/wikipedia.css"
      ]
    }
  ]
}