manifest.json

{
  "manifest_version": 3,
  "name": "otp-fetcher-extension",
  "version": "1.0",
  "description": "Interact with Gmail API",
  "permissions": [
    "scripting",
    "identity",
    "storage",
    "activeTab",
    "clipboardRead",
    "https://mail.google.com/",
    "https://www.googleapis.com/"
  ],
  "action": {
    "default_popup": "popup.html",
    "default_icon": {
      "16": "data/icons/glasses-svgrepo-com.png"
    }
  },
  "content_scripts": [
    {
      "matches": ["https://*/*"],
      "run_at": "document_start",
      "js": ["popup.js"]
    }
  ],

  "web_accessible_resources": [
    {
      "resources": ["popup.js", "api.js", "client.js", "api_child.js"],
      "matches": ["https://*/*"]
    }
  ],

  "oauth2": {
    "client_id": "<Enter your oauth(chrome extension)client id>",
    "scopes": ["https://www.googleapis.com/auth/gmail.readonly"]
  }
}