Examine source code of Get current week number

{
  "manifest_version": 2,
  "name": "Get current week number",
  "version": "3.0.0",
  "description": "Shows the current week number, in the extension icon and popup. Useful for sortin notes in for example OneNote",
  "icons": {
    "16": "icons/icon-week.svg",
    "48": "icons/icon-week.svg",
    "128": "icons/icon-week.svg"
  },
  "permissions": [
    "activeTab",
    "storage",
    "clipboardWrite"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_action": {
    "default_icon": "icons/icon-week.svg",
    "default_title": "Week Number",
    "default_popup": "popup/index.html"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{d124eb56-3e2e-41e3-aca1-808c6581d25d}"
    }
  }
}