Examine source code of PHP Pretifier

{
  "manifest_version": 2,
  "name": "PHP Pretifier",
  "version": "1.0",
  "description": "pretify error messages for php scripts",
  "web_accessible_resources": [
    "phpPretifier/warning-icon.svg",
    "phpPretifier/notice-icon.svg"
  ],
  "icons": {
    "48": "phpPretifier/48.png",
    "96": "phpPretifier/96.png"
  },
  "content_scripts": [
    {
      "matches": [
        "http://localhost/*"
      ],
      "js": [
        "phpPretifier/script.js"
      ],
      "css": [
        "phpPretifier/styles.css"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{8f277127-c1b5-4053-bf37-b4819706385d}"
    }
  }
}