Examine source code of They

{
  "manifest_version": 2,
  "name": "They",
  "version": "1",
  "description": "Replaces \"he or she\" and variations thereof with the gender neutral term \"they\".",
  "icons": {
    "64": "icons/64.png"
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "run_at": "document_end",
      "js": [
        "replace.js"
      ]
    }
  ]
}