Examine source code of CustomFireTab

{
  "manifest_version" : 2 ,
  "name" : "Custom FireTab URL",
  "version" : "1.4.0",
  "description" : "Set custom URLs for new tabs. Manage multiple URLs and choose your active homepage.",
  "author": "BigStrib",
  "icons" : {
    "48" : "icons/icon-48.png",
    "96" : "icons/icon-96.png",
    "128" : "icons/icon-128.png"
  },
  "permissions" : [
    "storage" ,
    "tabs" ,
    "webNavigation" 
  ],
  "background" : {
    "scripts" : [
      "background.js" 
    ]
  },
  "browser_action" : {
    "default_popup" : "popup.html",
    "default_icon" : "icons/icon-48.png"
  },
  "chrome_url_overrides" : {
    "newtab" : "newtab.html"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "BCS6131990@blake.com",
      "strict_min_version": "79.0",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  }
}