Examine source code of ProtonDB for Steam

{
  "manifest_version": 2,
  "name": "ProtonDB for Steam",
  "version": "2.3.0",
  "description": "Shows ratings from protondb.com on Steam",
  "permissions": [
    "https://www.protondb.com/*"
  ],
  "icons": {
    "48": "assets/icon-48.png",
    "96": "assets/icon-96.png"
  },
  "content_scripts": [
    {
      "matches": [
        "https://store.steampowered.com/app/*"
      ],
      "js": [
        "js/lib.js",
        "js/app.js"
      ],
      "css": [
        "assets/protondb.css"
      ]
    },
    {
      "matches": [
        "https://store.steampowered.com/wishlist/*"
      ],
      "js": [
        "js/lib.js",
        "js/wishlist.js"
      ],
      "css": [
        "assets/protondb.css"
      ]
    },
    {
      "matches": [
        "https://steamcommunity.com/id/*/games",
        "https://steamcommunity.com/id/*/games?tab=*"
      ],
      "js": [
        "js/lib.js",
        "js/games.js"
      ],
      "css": [
        "assets/protondb.css"
      ]
    }
  ],
  "background": {
    "scripts": [
      "js/background.js"
    ],
    "persistent": false
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{30280527-c46c-4e03-bb16-2e3ed94fa57c}"
    },
    "gecko_android": {}
  }
}