Examine source code of EndTab

{
  "manifest_version": 2,
  "name": "EndTab",
  "version": "1.2",
  "icons": {
    "48": "./icons/log48_2.png"
  },
  "permissions": [
    "tabs"
  ],
  "applications": {
    "gecko": {
      "id": "masterharoldsaxon4@gmail.com",
      "strict_min_version": "55.0"
    }
  },
  "browser_action": {
    "default_icon": {
      "48": "./icons/log48_2.png"
    },
    "default_title": "EndTab"
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  }
}