Examine source code of Alt Text Viewer Web

{
  "manifest_version": 2,
  "name": "Alt Text Viewer",
  "version": "2.0",
  "description": "Displays ALTs of images.",
  "icons": {
    "48": "icon.png"
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content.js"
      ],
      "css": [
        "styles.css"
      ]
    }
  ],
  "permissions": [
    "activeTab"
  ],
  "browser_action": {
    "default_icon": "icon.png",
    "default_title": "Turn On/Off ALTs"
  },
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": false
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{2c85e245-250a-445e-aa78-2b86385ea2d3}"
    }
  }
}