Examine source code of Image Size on Hover

{
  "manifest_version": 2,
  "name": "Image Size on Hover",
  "version": "2.0",
  "description": "Cool extension",
  "permissions": [
    "storage"
  ],
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content.js"
      ],
      "run_at": "document_idle"
    }
  ],
  "browser_action": {
    "default_popup": "popup.html",
    "default_title": "Image Size on Hover"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "image-size-on-hover@03e1ec2c-e03f-4754-b066-f692b471f311monkey.com",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  }
}