Examine source code of Whatsapp Chat Start

{
  "manifest_version": 2,
  "name": "__MSG_extensionName__",
  "description": "__MSG_extensionDescription__",
  "version": "0.2",
  "icons": {
    "48": "assets/icons/icon1_48px.png",
    "96": "assets/icons/icon1_96px.png"
  },
  "browser_action": {
    "default_icon": {
      "48": "assets/icons/icon1_48px.png",
      "96": "assets/icons/icon1_96px.png"
    },
    "default_title": "__MSG_extensionName__",
    "default_popup": "popup/new_chat.html"
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "permissions": [
    "storage"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "whatsapp-chat-start@ayasinakalin"
    }
  },
  "default_locale": "en"
}