Examine source code of Telegraph Dark Theme

{
  "description": "Adds a dark theme for the telegra.ph website.",
  "manifest_version": 2,
  "name": "Telegraph Dark Theme",
  "version": "1.2",
  "homepage_url": "https://github.com/3epo/telegraph-dark-mode",
  "icons": {
    "48": "icons/telegraph-48.png"
  },
  "content_scripts": [
    {
      "matches": [
        "*://telegra.ph/*"
      ],
      "js": [
        "insert.js"
      ],
      "css": [
        "style.css"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{de3630ea-aca7-48e8-a8e5-7e9babeb7997}"
    }
  }
}