Examine source code of Simple Calendar

{
  "manifest_version": 2,
  "name": "Simple Calendar",
  "version": "1.0",
  "description": "A clean calendar displaying the current month with navigation, highlighting today's date.",
  "permissions": [],
  "browser_action": {
    "default_popup": "popup.html",
    "default_title": "Simple Calendar"
  },
  "icons": {
    "48": "icon.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{913bcef1-f023-4ec7-b23f-c04b6bb6657b}"
    }
  }
}