Examine source code of ESEA filter

{
  "manifest_version": 2,
  "name": "ESEA filter",
  "description": "A basic extension to ESEA seasons' ladderboards!",
  "version": "1.3.1",
  "author": "https://github.com/marqdevx",
  "permissions": [
    "https://play.esea.net/league/standings*"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{b4a22bf1-06dc-490e-893d-1c5b233cb0db}",
      "strict_min_version": "78.0"
    }
  },
  "content_scripts": [
    {
      "matches": [
        "*://*.play.esea.net/*"
      ],
      "js": [
        "eseaFilter.js"
      ]
    }
  ]
}