Examine source code of Mobile Fullscreen Overlay

{
  "manifest_version": 2,
  "name": "Mobile Fullscreen Overlay",
  "short_name": "MFullscreen",
  "version": "1.1",
  "description": "Displays an on-page fullscreen overlay button that uses the standard Fullscreen API. The overlay automatically hides when hovered.",
  "author": "Fadhil JT",
  "icons": {
    "48": "icons/icon-48.png",
    "96": "icons/icon-96.png"
  },
  "browser_action": {
    "browser_style": false,
    "default_title": "Mobile Fullscreen",
    "default_icon": {
      "16": "icons/icon-16.png",
      "32": "icons/icon-32.png"
    }
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content.js"
      ],
      "run_at": "document_idle"
    }
  ],
  "permissions": [
    "activeTab",
    "<all_urls>"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "mobilefullscreen-overlay@fadhiljt",
      "strict_min_version": "140.0",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    },
    "gecko_android": {
      "strict_min_version": "142.0"
    }
  }
}