Examine source code of WA Self Messenger

{
  "update_url": "https://clients2.google.com/service/update2/crx",
  "manifest_version": 2,
  "permissions": [
    "storage"
  ],
  "name": "WA Self Messenger - Free Messages Sender",
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "content_scripts": [
    {
      "js": [
        "jquery.js",
        "content.js"
      ],
      "matches": [
        "https://web.whatsapp.com/*"
      ]
    }
  ],
  "description": "Send Whatsapp message to a single user or to users in sum without saving number",
  "icons": {
    "16": "img/icon.png",
    "48": "img/icon.png",
    "128": "img/icon.png"
  },
  "version": "2.6",
  "browser_action": {
    "default_icon": "img/icon.png",
    "default_popup": "popup.html",
    "default_title": "WA Self Messenger"
  }
}