Examine source code of File form filler

{
  "name": "CSV form filler",
  "version": "1.4.2",
  "description": "Extension to form filling by uploaded csv",
  "permissions": [
    "activeTab",
    "scripting"
  ],
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "js/fillFormsSimple.js",
        "js/fillMultipleForms.js",
        "js/generateFile.js",
        "js/fillWithGeneratedFile.js"
      ]
    }
  ],
  "action": {
    "default_popup": "popup.html"
  },
  "manifest_version": 3,
  "icons": {
    "128": "assets/images/iconOnly.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "csv.filler@gmail.com"
    }
  }
}