Examine source code of Japscan Dark Theme

{
  "manifest_version": 2,
  "name": "Japscan Dark Theme",
  "version": "1.0",
  "author": "Xiral",
  "description": "Dark theme pour le site Japscan uniquement lors de la lecture",
  "content_scripts": [
    {
      "matches": [
        "*://www.japscan.to/lecture-en-ligne/*"
      ],
      "js": [
        "darktheme.js"
      ]
    }
  ]
}