Examine source code of gForms Date Picker

{
  "manifest_version": 2,
  "name": "gForms Date Picker",
  "version": "1.0.0",
  "description": "Adds a convenient date picker beside date fields in Google Forms for easier date selection",
  "homepage_url": "https://github.com/masumulhassan/gforms-datepicker",
  "icons": {
    "48": "icons/icon-48.png",
    "96": "icons/icon-96.png"
  },
  "content_scripts": [
    {
      "matches": [
        "*://docs.google.com/forms/*"
      ],
      "js": [
        "content_scripts/datepicker.js"
      ],
      "run_at": "document_end"
    }
  ],
  "permissions": [
    "activeTab"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "gformdatepicker@masum.me"
    }
  }
}