Examine source code of Event Countdown

{
  "manifest_version": 2,
  "name": "Event Countdown",
  "description": "Count down to what matters: birthdays, deadlines and trips with days remaining on the toolbar badge.",
  "version": "3.0.1.2",
  "browser_specific_settings": {
    "gecko": {
      "id": "{86d7e9ca-ca9e-4f98-894b-8644d2497ced}",
      "strict_min_version": "101.0",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  },
  "icons": {
    "32": "graphics/icon-32.png",
    "48": "graphics/icon-48.png",
    "64": "graphics/icon-64.png",
    "96": "graphics/icon-96.png",
    "128": "graphics/icon-128.png"
  },
  "permissions": [
    "storage"
  ],
  "background": {
    "scripts": [
      "src/core.js",
      "src/background.js"
    ]
  },
  "browser_action": {
    "default_title": "Event Countdown",
    "default_popup": "src/popup.html",
    "default_icon": {
      "32": "graphics/icon-32.png",
      "48": "graphics/icon-48.png",
      "64": "graphics/icon-64.png",
      "96": "graphics/icon-96.png",
      "128": "graphics/icon-128.png"
    }
  }
}