Examine source code of Hide my username

{
  "manifest_version": 2,
  "version": "1.0",
  "description": "An extension to hide Username to site.",
  "name": "Hide my username",
  "content_scripts": [
    {
      "matches": [
        "*://*/*"
      ],
      "js": [
        "content.js"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{bb3670eb-f148-4431-88bd-4c5750cf2429}"
    }
  }
}