Examine source code of Sync Everything

{
  "description": "A Firefox Extension to synchronize video playback between P2P devices",
  "manifest_version": 2,
  "name": "Sync Everything",
  "version": "1.1",
  "homepage_url": "https://github.com/kaangiray26/sync_ext",
  "icons": {
    "48": "icons/48.png"
  },
  "permissions": [
    "activeTab"
  ],
  "browser_action": {
    "default_icon": {
      "48": "icons/48.png"
    },
    "default_title": "Sync Everything",
    "default_popup": "/popup/index.html"
  },
  "background": {
    "page": "background.html"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{9905f9fa-ff7b-420d-9d92-a048e7fe67f4}"
    }
  }
}