Examine source code of Json Viewer FF

{
  "manifest_version": 2,
  "name": "JSON Viewer",
  "description": "A beautiful JSON formatter for Chrome",
  "version": "1.1.1",
  "icons": {
    "16": "icon/16.png",
    "32": "icon/32.png",
    "48": "icon/48.png",
    "96": "icon/96.png",
    "128": "icon/128.png"
  },
  "permissions": [
    "storage",
    "<all_urls>"
  ],
  "browser_specific_settings": {
    "gecko": {
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      },
      "id": "{e8af7d1d-52ac-47d8-817b-c36d0df4bd49}"
    }
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_action": {
    "default_title": "JSON Viewer",
    "default_popup": "popup.html"
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "run_at": "document_idle",
      "js": [
        "content-scripts/content.js"
      ]
    }
  ]
}