Examine source code of The Old Reader Dark

{
  "manifest_version": 2,
  "name": "The Old Reader Dark",
  "short_name": "the-old-reader-dark",
  "version": "0.4",
  "description": "Dark theme for The Old Reader.",
  "homepage_url": "https://github.com/laedit/the-old-reader-dark",
  "permissions": [
    "*://theoldreader.com/*",
    "storage"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "content_scripts": [
    {
      "run_at": "document_start",
      "matches": [
        "*://theoldreader.com/*"
      ],
      "css": [
        "content_scripts/dark-theme.css"
      ],
      "js": [
        "content_scripts/inject-css.js"
      ]
    }
  ],
  "icons": {
    "64": "icons/icon.png",
    "128": "icons/icon-128.png"
  },
  "options_ui": {
    "page": "options.html",
    "browser_style": true
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{bd10894f-7ece-4d91-b678-53fa508b9e6a}",
      "strict_min_version": "57.0"
    }
  }
}