Examine source code of Rainbowify

{
  "manifest_version": 2,
  "name": "BorderifyXDv2",
  "version": "1.1",
  "description": "Dodaje tęczę wszędzie gdzie się da",
  "icons": {
    "48": "icons/icon.png"
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "css": [
        "rainbow.css"
      ]
    }
  ]
}