Examine source code of Proton City

{
  "manifest_version": 2,
  "name": "Proton City",
  "version": "1.1resigned1",
  "description": "Adds Proton City compatibility scores to Steam store pages.",
  "content_scripts": [
    {
      "matches": [
        "*://store.steampowered.com/app/*"
      ],
      "js": [
        "inject.js"
      ]
    }
  ],
  "icons": {
    "48": "icon.png"
  },
  "permissions": [
    "*://proton.city/*"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{af60b82c-9be1-4041-bac4-97ed4dd602db}"
    }
  }
}