Examine source code of ESEA Rank

{
  "name": "ESEA Ranks",
  "version": "1.2",
  "description": "Shows player ranks & MMR on match pages",
  "permissions": [
    "webNavigation",
    "*://play.esea.net/*"
  ],
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": false
  },
  "content_scripts": [
    {
      "matches": [
        "*://play.esea.net/*"
      ],
      "js": [
        "esea.js"
      ]
    }
  ],
  "manifest_version": 2
}