Examine source code of OP.GG Darkmode

{
  "manifest_version": 2,
  "name": "OP.GG Darkmode",
  "version": "1.3.4",
  "description": "Enable darkmode on op.gg",
  "icons": {
    "64": "icons/icon_64.png",
    "128": "icons/icon_128.png",
    "256": "icons/icon_256.png"
  },
  "content_scripts": [
    {
      "matches": [
        "*://*.op.gg/*"
      ],
      "js": [
        "darkness.js"
      ],
      "run_at": "document_start"
    }
  ],
  "permissions": [
    "*://op.gg/*",
    "*://www.op.gg/*",
    "*://euw.op.gg/*",
    "*://eune.op.gg/*",
    "*://lan.op.gg/*",
    "*://jp.op.gg/*",
    "*://oce.op.gg/*",
    "*://ru.op.gg/*",
    "*://na.op.gg/*",
    "*://br.op.gg/*",
    "*://tr.op.gg/*",
    "*://las.op.gg/*",
    "*://sg.op.gg/*",
    "*://id.op.gg/*",
    "*://ph.op.gg/*",
    "*://tw.op.gg/*",
    "*://vn.op.gg/*",
    "*://th.op.gg/*"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{4d065466-3509-4355-a77e-15b2c73cd11f}"
    }
  }
}