Examine source code of ZenFocus

{
  "manifest_version": 2,
  "name": "ZenFocus",
  "version": "1.0",
  "description": "Hide distracting UI elements on study platforms for better focus.",
  "icons": {
    "48": "icon.png"
  },
  "content_scripts": [
    {
      "matches": [
        "*://*.youtube.com/*",
        "*://*.facebook.com/*"
      ],
      "js": [
        "content.js"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "zenfocus@example.com",
      "strict_min_version": "58.0"
    }
  }
}