Examine source code of Hide Images (Opacity)

{
  "name": "Hide Images (Opacity)",
  "description": "Hide all the images on the page (using opacity). Optionally, you can configure to display the images on mouse over.",
  "version": "2.4",
  "manifest_version": 2,
  "permissions": [
    "storage",
    "tabs",
    "activeTab",
    "<all_urls>"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "icons": {
    "48": "icons/hide.png"
  },
  "browser_action": {
    "default_icon": "icons/hide.png",
    "default_title": "Hide Images"
  },
  "options_ui": {
    "page": "options/options.html"
  },
  "commands": {
    "_execute_browser_action": {
      "suggested_key": {
        "default": "Alt+0"
      },
      "description": "Hide Images"
    }
  }
}