Examine source code of Otto Numbers FF

{
  "manifest_version": 2,
  "name": "Otto Numbers for Firefox",
  "version": "1.0.1",
  "description": "Adds ranking indicators next to Twitch streamers' names, showing their revenue ranking over the last two years",
  "content_scripts": [
    {
      "matches": [
        "https://*.twitch.tv/*"
      ],
      "css": [
        "styles.css"
      ],
      "js": [
        "script.js"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{e89e7418-7e14-43d2-bf15-f438afd63ee1}"
    }
  }
}