Examine source code of Calendarium

{
  "manifest_version": 3,
  "name": "__MSG_extension_name__",
  "description": "__MSG_extension_description__",
  "version": "1.9.0",
  "default_locale": "en",
  "browser_specific_settings": {
    "gecko": {
      "id": "calendarium@kami911.firefox",
      "strict_min_version": "140.0",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    },
    "gecko_android": {
      "strict_min_version": "142.0"
    }
  },
  "icons": {
    "48": "icons/icon-48.png",
    "96": "icons/icon-96.png",
    "128": "icons/icon-128.png"
  },
  "chrome_url_overrides": {
    "newtab": "newtab.html"
  },
  "chrome_settings_overrides": {
    "homepage": "newtab.html"
  },
  "action": {
    "default_popup": "popup.html",
    "default_icon": {
      "48": "icons/icon-48.png",
      "96": "icons/icon-96.png",
      "128": "icons/icon-128.png"
    },
    "default_title": "Calendarium"
  },
  "background": {
    "scripts": [
      "background.js"
    ],
    "type": "module"
  },
  "options_ui": {
    "page": "options.html",
    "open_in_tab": true
  },
  "commands": {
    "open-full-view": {
      "suggested_key": {
        "default": "Ctrl+Shift+Y",
        "mac": "Command+Shift+Y"
      },
      "description": "Open Calendarium's full view in a new tab"
    }
  },
  "permissions": [
    "storage",
    "alarms",
    "search",
    "menus",
    "theme"
  ],
  "optional_host_permissions": [
    "https://api.wikimedia.org/*",
    "https://api.open-meteo.com/*"
  ]
}