Examine source code of NowIs.Org > Calendar

{
  "manifest_version": 2,
  "name": "NowIs.Org > Calendar",
  "version": "1.0",
  "description": "Add events from now-is.org to your google calendar",
  "permissions": [
    "storage",
    "activeTab"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "nowis-calendar@pedrolopes.org",
      "data_collection_permissions": {
        "required": [
          "websiteContent"
        ]
      }
    }
  },
  "options_ui": {
    "page": "options.html",
    "open_in_tab": true
  },
  "content_scripts": [
    {
      "matches": [
        "https://now-is.org/"
      ],
      "js": [
        "content.js"
      ]
    }
  ]
}