Examine source code of Hidden Eye

{
  "name": "Hidden Eye",
  "description": "hide/view HTML elements on a web page.",
  "version": "2.0.0",
  "manifest_version": 2,
  "browser_action": {
    "default_popup": "./views/index.html",
    "default_icon": {
      "16": "/assets/icon_128.png",
      "32": "/assets/icon_128.png",
      "48": "/assets/icon_128.png",
      "128": "/assets/icon_128.png"
    }
  },
  "options_ui": {
    "page": "/views/options.html",
    "open_in_tab": true
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content.js"
      ]
    }
  ],
  "icons": {
    "16": "/assets/icon_128.png",
    "32": "/assets/icon_128.png",
    "48": "/assets/icon_128.png",
    "128": "/assets/icon_128.png"
  },
  "web_accessible_resources": [
    "./assets/*"
  ],
  "permissions": [
    "storage",
    "tabs",
    "activeTab"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{db2db699-6b2d-432c-8e9b-b87e199244c8}"
    }
  }
}