Examine source code of Bracket Balance Checker

{
  "manifest_version": 2,
  "name": "Bracket Balance Checker",
  "version": "1.0",
  "description": "A Mozilla add-on to check if an expression is balanced.",
  "icons": {
    "48": "icon.png"
  },
  "content_scripts": [
    {
      "matches": [
        "*://*/*"
      ],
      "js": [
        "popup.js"
      ],
      "css": [
        "popup.css"
      ]
    }
  ],
  "permissions": [
    "activeTab"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{fbcb3576-a969-4212-b052-5d8ef993d93f}"
    }
  }
}