Examine source code of Page Dimmer

{
  "manifest_version": 2,
  "name": "Page Dimmer",
  "version": "1.0",
  "description": "Adjust the opacity of any webpage to reduce eye strain.",
  "permissions": [
    "activeTab"
  ],
  "browser_action": {
    "default_icon": "icons/dimmer-48.png",
    "default_popup": "popup.html",
    "default_title": "Page Dimmer"
  },
  "icons": {
    "48": "icons/dimmer-48.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{9b813f43-91bc-4c3e-84d3-24afea022ea2}"
    }
  }
}