Examine source code of Steam Pixel

{
  "manifest_version": 2,
  "name": "Steam Pixel",
  "version": "0.3.1",
  "description": "Quicly access the Steam App, SteamDB, ProtonDB or Steam Card Exchange from the game page.",
  "icons": {
    "48": "assets/steam-48.png"
  },
  "content_scripts": [
    {
      "matches": [
        "*://*.steampowered.com/app/*"
      ],
      "js": [
        "steamPixel.js"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{612367b5-26a0-407c-886c-7ea44fbc974e}"
    }
  }
}