Examine source code of Steam HLTB

{
  "manifest_version": 2,
  "name": "Steam HLTB",
  "description": "A browser extension to show HowLongToBeat times on Steam game store pages",
  "version": "0.0.2",
  "icons": {
    "16": "icons/16.png",
    "32": "icons/32.png",
    "48": "icons/48.png",
    "128": "icons/128.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{ec5eff8f-acb7-4556-bb87-a92808e3a10d}",
      "data_collection_permissions": {
        "required": [
          "browsingActivity"
        ]
      }
    }
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "content_scripts": [
    {
      "matches": [
        "*://store.steampowered.com/app/*"
      ],
      "run_at": "document_idle",
      "js": [
        "content-scripts/content.js"
      ]
    }
  ],
  "browser_action": {},
  "permissions": [
    "https://hltbapi.codepotatoes.de/*"
  ]
}